Tuesday

May 26, 2015

May 26, 2015

Number of results: 17,117

**help~MATHS**

Let S be the set of {(1,0),(0,1),(1,1),(1,−1),(−1,1)}-lattice path which begin at (1,1), do not use the same vertex twice, and never touch either the x-axis or the y-axis. Let Px,y be the number of paths in S which end at the point (x,y). Determine P2,4. Details ...
*May 23, 2013 by SOmebody*

**sd224**

Let S be the set of {(1,0),(0,1),(1,1),(1,−1),(−1,1)}-lattice path which begin at (1,1), do not use the same vertex twice, and never touch either the x-axis or the y-axis. Let Px,y be the number of paths in S which end at the point (x,y). Determine P2,4. Details ...
*June 30, 2013 by doeom*

**Chemistry**

Determine for solid manganese (Mn) the following: What is the atomic density (atoms/m) along the [110] direction of the Mn crystal? What are the number of nearest neighbors around an atom in the Mn crystal? Calculate the interplanar spacing (m) between {220} planes in the Mn ...
*November 15, 2013 by koala*

**Chemistry**

Determine for solid manganese (Mn) the following: What is the atomic density (atoms/m) along the [110] direction of the Mn crystal? What are the number of nearest neighbors around an atom in the Mn crystal? Calculate the interplanar spacing (m) between {220} planes in the Mn ...
*August 26, 2014 by 3091*

**chemistry**

Ionic compounds at room temperature usually exist as solids with distinct crystalline lattice structures. True False I think true
*November 10, 2012 by Keri*

**chemistry**

In a laboratory experiment, the density of a concentrated sugar solution was determined by measuring the volume of the solution and corresponding mass. Three students each made a set of measurements using a different balance and used the results to calculate density. Their ...
*August 30, 2008 by helpp*

**chemistry**

Please help. My teacher never went over crystal lattices and the book doesn't cover it either :( Copper crystallizes in a face-centered cubic lattice. If the edge of the unit cell is 351pm, what is the radius of the copper atom?
*December 10, 2012 by Jess*

**architecture**

what is space? what does mean a space structure? what is spacer?
*June 21, 2014 by gutema *

**Physics**

Electrons in a beam incident on a crystal at an angle of 30ͦ have kinetic energies ranging from zero to a maximum of 5500 eV. The crystal has a grating space d=0.5 Aͦ, and the reflected electrons are passed through a slit .Find the velocities of the electrons passing...
*April 7, 2011 by Abby*

**Physics**

Electrons in a beam incident on a crystal at an angle of 30ͦ have kinetic energies ranging from zero to a maximum of 5500 eV. The crystal has a grating space d=0.5 Aͦ, and the reflected electrons are passed through a slit .Find the velocities of the electrons passing...
*April 8, 2011 by Vanda*

**Physics urgent!!!!**

Electrons in a beam incident on a crystal at an angle of 30ͦ have kinetic energies ranging from zero to a maximum of 5500 eV. The crystal has a grating space d=0.5 Aͦ, and the reflected electrons are passed through a slit .Find the velocities of the electrons passing...
*April 8, 2011 by Vanda*

**chemistry(check my answer)**

how do resonance structure related to its real structure? resonance structure is just another way to write the lewis dot with different formal charges and bond order
*April 8, 2010 by phys*

**math**

Let S be the set of {(1,1), (1,−1), (−1,1), (1,0), (0,1)}-lattice paths which begin at (1,1), do not use the same vertex twice, and never touch either the x-axis or the y-axis. Let Sx,y be the set of paths in S which end at (x,y).For how many ordered pairs (x,y) ...
*July 23, 2013 by andy*

**math**

Let S be the set of {(1,1), (1,−1), (−1,1), (1,0), (0,1)}-lattice paths which begin at (1,1), do not use the same vertex twice, and never touch either the x-axis or the y-axis. Let Sx,y be the set of paths in S which end at (x,y).For how many ordered pairs (x,y) ...
*July 24, 2013 by Anonymous*

**Chemistry**

Two atoms with charges of +1 and -1 are separated by a distance of 0.5 angstroms. What would happen to the lattice energy between ions if the distance increases to 2 angstroms? A. The lattice energy decreases by a factor of 4. B. The lattice energy increases by a factor of 16...
*April 19, 2015 by Cortney*

**lattice point**

A lattice point is an ordered pair (x, y) where both x and y are integers. A triangle is formed by the three points (1, 1), (9, 1) and (9, n). For what integer value of n 0 are there exactly 560 lattice points strictly in the interior of the triangle?
*June 27, 2012 by Anonymous*

**Chemistry**

The crystal structure of lithium sulfide (Li2S) is pictured here. The length of the unit cell is 5.88 x 10^2. For this structure, determine: a)the coordination number of Li and S b) the number of formula nunits in the unit cell c) the density of Li2S
*April 15, 2009 by Erica*

**chemistry**

I need to find out which structure is more correct: Reaction of the compound C3H8O with CrO3 (oxidizing agent) yields acetone. Which of the three structures is more correct? (My three structures are as follows: 1-propanol, 2-propanol, and methylethyl ether.)
*January 18, 2011 by ella*

**Chemistry**

27. Amorphous solids have crystal structures.- F? 32. Pure, crystalline solids freeze and melt at the same temperature.- F 34. Water expands as it freezes.- T Thanks -MC
*October 26, 2010 by mysterychicken*

**physics**

why we cannot use visible light for studying the crystal structure using Bragg’s diffraction method?
*May 19, 2011 by diwakar*

**BIOLOGY**

how does the structure of DNA contribute to the accurate transmission of hereditary material? hereditary material Not much help courtney. I'd say its structure utilizing vanderwahls forces allows it to have a quaternary structure which takes up less space. (tightly coiled) Try...
*November 20, 2006 by Alex- hlp plz*

**CHEM**

the number of nonbonding electrons exceeds the number of bonding electrons in the lewis structure of which of the following molecules? I am having a problem with the Lewis structures. HCN NH3 H2O please explain the structure thank you so much
*February 25, 2014 by layla*

**ap chem**

There are several oxides of nitrogen; among the most common are N2O, NO, and NO2. 1.Write the Lewis structures for each of these molecules. In each case the oxygens are terminal atoms. 2. Which of these molecules "violate" the octet rule? 3. Draw resonance structures for N2O. ...
*January 9, 2007 by Justyna*

**science**

Can some one help me I don’t know what to take out from the aspirin molecule, for the following structures? I have to generate a copy of the molecular structure of aspirin and then for each of the molecular features listed in (i) – (iii) have to produce a related structure ...
*June 29, 2007 by katie*

**Calculus**

In increasing order, rank: 3^ln 2, 2^3, 2^ln 3 *do not use a calculator, and explain your choices Obviously, 2^3=8 So, instinctively, I entered the other values into my calculator just to rank the quantities using decimal places. However, in my calculator, 3^ln 2 and 2^ln 3 ...
*October 3, 2010 by Jon*

**psychology**

The sentences, "Lee gave the ball to Lynne" and "Lynne received the ball from Lee," have the same: surface structure. syntax. surface and deep structures. deep structure. Does this sentence have both surface and deep structure? From reading my text book, I believe it does, but...
*October 31, 2010 by cindy*

**Chemistry**

KF has the same type of crystal structure as NaCl. The unit cell of KF has an edge length of 5.39 Å. Find the density of KF in g/cm3
*December 8, 2012 by Ian *

**Chemistry**

KF has the same type of crystal structure as NaCl. The unit cell of KF has an edge length of 5.39 Å. Find the density of KF in g/cm3
*December 8, 2012 by Ian *

**chemistry**

Answer the following for a primitive cubic unit cell. Answers should be numerical, set r = 7.0. edge in terms of r, the lattice pt radius=? face diagonal in terms of r, the lattice pt radius=? body diagonal in terms of r, the lattice pt radius=?
*February 16, 2009 by leah*

**Chemistry**

Rank the following compounds in order of their solubility in water. (most soluble = 1 -- least soluble = 4)--Note that for the same solubility rank the same (a tie). (CH3)2CHOH HOCH2CH(OH)CH2OH CH3CH2OH (CH3)3COH
*March 14, 2013 by Maddie*

**psychology**

The sentences," lee gave the ball to LYNNE" and Lynne received the ball from Lee,"have the same: a. surface structure b. syntax c. surface and deep structures d. deep structures I chose A, is that right?
*September 30, 2011 by bj*

**socology**

what is the meaning of ventilation and space of structures
*February 10, 2013 by tijani*

**maths**

How many lattice points lie on the sphere x^2+y^2+z^2=2013? Details and assumptions A lattice point has integer coordinates.
*April 3, 2013 by Anonymous*

**chem **

What is the name origin of plutonium? What is its crystal structure? What is the atomic number? Is it radio active or synthetic? What is its classification? What is its uses? Where is it obtained from?
*January 9, 2012 by lizzy*

**art**

Outline the main goals of Green Architecture, describing how one or several architects achieved each of those goals in a specific structure. Discuss the advantages and difficulties of Green Architecture in terms of meeting the functions of structures and the needs of those who...
*July 29, 2011 by Pebbles *

**Organic chemistry**

Write contributing (important) resonance structures for each of the following compounds and predict their relative C=O vibrational frequencies based on the importance of the contributing resonance structures. List in them order from highest to lowest frequency. a.) ...
*February 17, 2009 by Jane*

**Science**

1. Find the lattice parameter of pure iron at room temperature. 2. What is the ratio of the lattice parameter of the iron to the wavelength of the radiation used. 3. What is the value of two theta for the second peak? 4. By what factor is the lattice parameter of the Fe bigger...
*August 15, 2012 by Justin*

**physical**

Rank the following 3 classes of materials in order of increasing typical Young's Modulus: metals such as copper, plastics such as HDPE (high density polyethelene), and ceramics such as alumina (Al2O3). Do not look up the values of Young's Modulus, instead base your answer on ...
*April 4, 2013 by Anonymous*

**chemistry**

Rank from decreasing to increasing the effect the functional groups have on the melting point of compound x: -OH or -COOH i think its COOH<OH because OH is easier to hydrogen bond?
*December 2, 2008 by un*

**biology**

describe 2 structures of bacterial cells what they look like and their molecular structure
*January 13, 2010 by jessica*

**Chemistry**

Please help! Answer the following for a body centered unit cell. Crystalline Solids Program Answers should be numerical, set r = 4.0. edge in terms of r, the lattice pt radius: face diagonal in terms of r, the lattice pt radius: body diagonal in terms of r, the lattice pt radius:
*February 17, 2011 by Shawn*

**Chemistry**

Please help! Answer the following for a body centered unit cell. Crystalline Solids Program Answers should be numerical, set r = 4.0. edge in terms of r, the lattice pt radius: face diagonal in terms of r, the lattice pt radius: body diagonal in terms of r, the lattice pt radius:
*February 17, 2011 by Shawn*

**Biology**

Find a recent (from 2009 June onwards) and interesting article from the mass media with a theme that is related to topics learnt in Cell Biology. So far I've learnt Membrane Structure & function,Organelles and their structure & function, as well as their membrane systems, and ...
*February 17, 2010 by alex*

**science**

Answer the following for a body centered unit cell. Answers should be numerical, set r = 7.0. edge in terms of r, the lattice pt radius__? face diagonal in terms of r, the lattice pt radius__? body diagonal in terms of r, the lattice pt radius__?
*February 15, 2010 by HELP!*

**statistic**

Identify the level of measurement for the following? 1)What state/country were you born? 2)What is the temperature outside rigth now? 3)Rank all of the courses you are currently.The class you look most forward to taking will be rank one ,next two ,and so on . what is the rank ...
*July 13, 2011 by mike *

**chemistry**

Platinum has a face-centered cubic crystal structure and a density of 21.5 g/cm3. What is the radius of the platinum atom?
*January 29, 2010 by Fred*

**URGENT HELP: calculus - limits at inifinity**

1.The efficiency of an internal combustion engine is: efficiency (%) = 100 [1 - (1/(x/y)^c)] where x/y is the ratio of the uncompressed gas to the compressed gas and C is a positive constant dependent on the engine design. Find the LIMIT of the efficiency as the compression ...
*December 13, 2007 by Anonymous*

**Chemisty**

I do not know how to rank the polarity between these, i have also included the boiling point in degrees C but it still does not help. The only thing that i think is that D is the least polar because it is symmetrical, and i think A is the most but I'm not sure about the rest. ...
*August 12, 2014 by Polarity *

**Math**

Carrie and Crystal live at a equal distances from school. Carries walks to school at an average rate of 3 miles per hour and Crystal rides her bike at an avergae rate of 9 miles per hour. It takes Carrie 20 minutes longer than Crystal to get to school. How far do Crystal and ...
*March 20, 2010 by David*

**help needed !!! URGENT**

Can some one help me I don’t know what to take out from the aspirin molecule, for the following structures? I have to generate a copy of the molecular structure of aspirin and then for each of the molecular features listed in (i) – (iii) have to produce a related structure ...
*June 30, 2007 by kat*

**Biology**

Just need this checked: 'The cytoskeleton of eukaryotes serves many functions. One of these functions is served in prokaryotes by a different major structure. Which structural feature is it? How do these different structures serve the same function in the two cell types?' My ...
*February 5, 2010 by mysterychicken*

**CHEMISTRY**

the only property listed that is not characteristic of ionic compounds is A.high melting point. B.hardness. C.lack of crystal structure D.brittleness I will be happy to critique your thinking on this.
*January 12, 2007 by Darius Graham*

**Chemistry**

For the following crystals, explain how their melting points are related to the bonding forces and the crystal structure. Copper,Cu Water,H2O Sodium chloride,NaCl Diamond,C
*January 19, 2008 by Nancy*

**Chemistry**

For the following crystals, explain how their melting points are related to the bonding forces and the crystal structure. Copper,Cu Water,H2O Sodium chloride,NaCl Diamond,C
*January 20, 2008 by Nancy*

**ACT**

This is kinda of stupid question but I really need to know. What does class rank mean on ACT score report?? Is it the rank for ACT test takers in your school? or is it the rank for your grades in high school ??
*May 21, 2008 by gigi*

**english **

the sentences Lee gave the ball to Lynne and Lynne recieved the ball from Lee have the same: A surface structure B syntax C surface and deep structures D deep structure I was thinking is A but I am not sure
*September 16, 2009 by vedrana*

**psychology**

the sentences Lee gave the ball to Lynne and Lynne recieved the ball from Lee have the same: A surface structure B syntax C surface and deep structures D deep structure I was thinking is A but I am not sure
*September 16, 2009 by vedrana*

**Psychology**

The sentences, "Lee gave the ball to Lynne" and "Lynne received the ball from Lee," have the same: surface structure. syntax. surface and deep structures. deep structure. I am going for C Not Sure
*March 14, 2011 by Chloe*

**Science - Chemistr++++++++++++++++++++++++++++++++**

List materials that are commonly found at home or in school that have: a. Different structures and exhibit different properties b. The same chemical make-up (composition) but with different structures, hence, different properties c. The same properties but with different ...
*June 24, 2013 by Annika*

**Science-Chemistry**

List materials that are commonly found at home or in school that have: a. Different structures and exhibit different properties b. The same chemical make-up (composition) but with different structures, hence, different properties c. The same properties but with different ...
*June 24, 2013 by Annika*

**chemistry**

write the lewis structure for dinitrogen oxide. include the 2 resonance structures and formal charges where appropriate.
*September 20, 2010 by Missy*

**Chemistry**

r = 5.0. how do i find the following: -edge in terms of r, the lattice pt radius -face diagonal in terms of r, the lattice pt radius -body diagonal in terms of r, the lattice pt radius
*February 15, 2010 by Mary*

**chem**

Complete the table below: Answer the following for a body centered unit cell. (Hint: Helpful information can be found by going to the "Lattice" menu, choosing "Cubic", and then choosing "Body-Centered" in the Crystalline Solids program.) Crystalline Solids Program Answers ...
*February 21, 2011 by brian*

**chemistry**

Answer the following for a body centered unit cell. edge in terms of r, the lattice pt radius face diagonal in terms of r, the lattice pt radius body diagonal in terms of r, the lattice pt radius
*February 18, 2008 by Stacy*

**chemistry**

Answer the following for a face centered unit cell. r=6.0 edge in terms of r, the lattice pt radius face diagonal in terms of r, the lattice pt radius body diagonal in terms of r, the lattice pt radius
*February 18, 2008 by Kacy*

**Science/math**

BCC crystal structure, atomic radius of .1363, and an atomic weight of 95.94g/mol. How would you compute the theoretical density?
*September 15, 2009 by Z32*

**science**

Some hypothetical metal has the simple cubic crystal structure. If its atomic weight is 70.4 g/mol and the atomic radius is 0.126 nm, compute its density in g/cc.
*January 22, 2015 by Cam*

**chemistry**

when do you need to use the octet rule for lewis structures and when does it not apply i am confused for N2O4 i cant get the rules to work with the structure
*April 20, 2009 by lyne*

**English-Urgent please!**

What phrase structure rule creates coordinate structures? I am confused here. Is it prepositional phrases?
*December 21, 2013 by Student*

**College Chemistry**

Of KCl and NaCl, which has a higher lattice energy? What is lattice energy? Lost. Please help.
*October 24, 2010 by Sally*

**Ionic Crystal Structures**

Calculate the density of CsCl. Use 169pm as the radius of Cs+. rCs+= 169pm length= 2*169= 338pm= 3.38*10^-8 v= l^3= (3.38*10^-8)^3 = 3.86*10^-23 m= 2* 168.36 g/mol / 6.022*10^23 = 5.59*10^-24g d= m/v d= 5.59*10^-24g/ 3.86*10^-23 d= 14.48 g/cm^3 BUT the correct answer is 4.24 g...
*February 6, 2009 by --*

**Math**

Can someone help me with this problem? I don't understand lattice multiplication. Use lattice multiplication to find the product (Hint: Remember to estimate first!) 124*56. Thanks for your help.
*June 19, 2009 by B.B.*

**chemistry**

Vanadium crystalizes in a body centered cubic lattice (the V atoms occupy only the lattice points) how many V atoms are present in a unit cell?
*January 20, 2011 by Angela*

**Chemistry **

Why are metals malleable? A. Because they reflect incoming photons B. Because they are made of atoms that have tightly held electrons C. Because of their structure and uniform bonding in all directions D. Because their lattice energy is very high I think the answer is c but I ...
*December 16, 2014 by Morgan *

**science**

For the following crystals, explain how their melting points are related to the bonding forces and the crystal structure. a)Copper,Cu b)Water,H20 c)Sodium chloride,NaCl d)Diamond,C (Broken Link Removed)
*March 25, 2007 by lauren*

**CHEMISTRY**

I am confused about this statement about water Which of the following is TRUE regarding water only covalent bonds are broken when ice melts (dont think so) all of the staements (A-D) are false energy must be given off in order to break down the crystal lattice of ice to a ...
*May 11, 2010 by Andy*

**Chemistry (CHEM)**

Can someone explain the electrical conductivity of melted and of aqueous solutions of ionic compounds. An explain it using the characteristics of ionic compounds. ThankS A Whole lot.. In Advance I suggest you go to the site recommended by Ms.Sue. Here is a brief summary but ...
*November 14, 2006 by Brittany*

**Chemistry**

Rank Na, Mg and K in order of increasing 2nd ionization energy a. Na < K < Mg b. Mg < K < Na c. K < Na < Mg d. K < Mg < Na e. Mg < Na < K
*April 23, 2010 by Zacky *

**SCIENCE**

1. WHAT IS resonance 2. whAT to frequncy of a sound when a car approaches How is resonance used? One kind of resonance is chemical resonance in which several structures can be drawn to represent a compound an the "real" structure is a hybrid of all of the possible structures. ...
*December 13, 2006 by TAYLOR*

**Math**

For a normally distributed distribution of variable x, where the mean is 50, and standard deviation is 2.5, calculate: a) the percentile rank of x=45 b) the z-score of x=52.6 c) the percentile rank of x=58 d) the 29.12th percentile e) the 89.74th percentile f) the z-score of x...
*April 25, 2010 by Ally*

**Chemistry**

Would the following structures be polar or nonpolar? (Not applicable if the structure is an ion. Pick "ionic" in that case). SO2 N2O N3−
*April 10, 2010 by Johannie*

**chemistry**

Draw the dominant Lewis structure for NO2+. Note, that this ion is isoelectronic with CO2. How many double bonds does this resonance structures have?
*November 4, 2014 by john*

**Chemistry**

Answer the following for a face centered unit cell. r = 6.0. how do i find the following edge in terms of r, the lattice pt radius face diagonal in terms of r, the lattice pt radius body diagonal in terms of r, the lattice pt radius
*February 15, 2010 by Mary*

**math**

The density of a crystal is 2.65 grams per cubic centimeter. Ryan has a rectangular prism made of quartz. It measures 10 cm by 10 cm by 6 cm. Find the weight of this crystal in kilograms.
*April 6, 2011 by Dan*

**Dichotymus key...**

I just some tips and help with a dichotymus key I'm doing in anatomy. (i hope I'm spelling it correctly) concerning simple structures of the skeletal system. Well there are 4 main classifications i chose to use; projections/processes, depressions/pits, cavities/passageways, ...
*October 15, 2009 by Chrissy*

**Partial Differential Equations**

At the He-Ne laser wavelength (L= 632.8 nm) the refractive indices of crystal quartz are n o = 1.54264 and n e = 1.55171 calculated from its Sellmeier equation. The laser is incident from the air onto the surface of crystal quartz at an angle of incidence of 45 degrees. For ...
*November 12, 2013 by Joy*

**Chemistry-Science**

Answer the following for a primitive cubic unit cell. Answers should be numerical, set r = 8.0 -edge in terms of r, the lattice pt radius:___ -face diagonal in terms of r, the lattice pt radius:___ -body diagonal in terms of r, the lattice pt radius:___ Answer the following ...
*February 14, 2009 by Bliss*

**Chemistry**

Can someone please help me with these chemistry questions...I just don't get it! 1. Using the following elements, rank them in order of increasing melting points, based on the periodic trend for melting point: Sr, Mg, Be, Ba? Would it be Be, Mg, Sr, Ba or would it be Ba, Sr, ...
*September 16, 2009 by Taylor*

**Physics (Please Help)**

At the He-Ne laser wavelength (L= 632.8 nm) the refractive indices of crystal quartz are n o = 1.54264 and n e = 1.55171 calculated from its Sellmeier equation. The laser is incident from the air onto the surface of crystal quartz at an angle of incidence of 45 degrees. For ...
*November 13, 2013 by Joy*

**statistics**

In a class of 300 students, John’s rank was 40. Find his percentile rank
*January 24, 2015 by Anonymous*

**Physics check**

Rank the following transitions in order of low to high frequencies: 3-2; 4-3; 2-1; 5-4; 5-3; 3-1; 4-2. 5-3; 4-2; 3-1; 5-4; 4-3; 3-2; 2-1 ?
*April 12, 2008 by Jeny*

**Finance**

Atlantic Seafood has determined that $17,000 is the break-even level of earnings before interest and taxes for the two capital structures it is considering. The one structure consists of all equity with 12,000 shares of stock. The second structure consists of 9,000 shares of ...
*October 28, 2013 by Maureen*

**Biomaterials**

What is the theoretical density of tantalum (Ta) with the following characteristics: Crystal structure: BCC Atomic radius: 14.6 Angstroms Atomic weight: 180.9 g/mol density needs to be in g/cm^3
*May 22, 2012 by Nate*

**chemistry cp**

rank the following compiunds in order of increasing boiling points. a. CO b. C2H6 c. NH3
*March 25, 2015 by susie*

**Math - Trigonometry **

Let f(x) be a polynomial such that f(cos theta) = cos(4 theta) for all \theta. Find f(x). (This is essentially the same as finding cos(4 theta) in terms of cos theta; we structure the problem this way so that you can answer as a polynomial. Be sure to write your polynomial ...
*November 6, 2013 by Sam*

**chemistry**

Metals + cold water. Li, Na, K, Ca. Notes on reactions, equations or space? <<<< dont no what space or equations means. can someone help? Also, say order of reactivity.
*March 14, 2009 by Nabiha*

**Chemistry**

Order the following solids according to increasing lattice energy. HgI2, CdCl2, ZnCl2 Now I get how to sort of do it, but I do not get how to do it if I'm looking at its radius if they do not provide it in the question.
*February 21, 2010 by Josh*

**math**

can someone make a lattice table. i have to multiply 523*73 using lattice multiplication. i know how to do it and have the numbers plugged in but without the table.
*April 9, 2010 by jennifer*

**Science**

The bonds between ions of opposite charge is strongest when the ions are small, the lattice energy of LiF is more exothermic than the lattice energy of CsI. Explain.
*March 23, 2012 by Godswill*

**chemistry**

the lattice energy for MgCl2 is -2326 kj/mol, which is much higher than that for NaCl which has a lattice energy of -786 kj/mol. Why is this so? Give at least two contributing factors.
*April 3, 2014 by Mai*