Popular questions and responses by Bob
  1. Economics

    A monopoly firm faces a demand curve given by the following equation: P = $500 − 10Q, where Q equals quantity sold per day. Its marginal cost curve is MC = $100 per day. Assume that the firm faces no fixed cost. You may wish to arrive at the answers

    asked on May 3, 2016
  2. Chemistry

    Assuming that sea water is a 3.5 wt % solution of NaCl in water, calculate its osmotic pressure at 20°C. The density of a 3.5% NaCl solution at 20°C is 1.023 g/mL.

    asked on April 13, 2010
  3. Pre Calculus

    Find all $2 \times 2$ matrices $\bold{A}$ that have the property that for any $2 \times 2$ matrix $\bold{B}$, \[\bold{A} \bold{B} = \bold{B} \bold{A}.\]

    asked on September 20, 2017
  4. math

    I look at a random time of day at a digital clock (that shows times from 1:00 through 12:59). What is the probability that (ignoring the colon) I see a palindrome such as 8:08? Express your answer as a common fraction.

    asked on November 15, 2012
  5. Chemistry

    Balance the following equation for a half reaction that occurs in basic solution. Use e– as the symbol for an electron. SO3^2- ---> S2O4^2-

    asked on May 4, 2014
  6. LCM of two numbers?

    lcm of two numbers pi/3 pi/2 How do I do it? Would it be pi or pi/6? Thanks

    asked on December 15, 2013
  7. Microecon help

    Please help! Review for a test and am so lost! (1) An article in the New York Times (Oct. 18, 1990) described a successful marketing campaign by the French champagne industry. The article also noted that “many executives felt giddy about the

    asked on September 3, 2007
  8. Chemistry

    The equilibrium constant, Kp, equals 3.40 for the isomerization reaction: cis-2-butene trans-2-butene. If a flask initially contains 0.250 atm of cis-2-butene and 0.145 atm of trans-2-butene, what is the equilibrium pressure of each gas?

    asked on December 2, 2014
  9. Chemistry

    Kc is 1.67 × 1020 at 25°C for the formation of iron(III) oxalate complex ion: Fe3+(aq) + 3 C2O42-(aq) [Fe(C2O4)3]3-(aq). If 0.0200 M Fe3+ is initially mixed with 1.00 M oxalate ion, what is the concentration of Fe3+ ion at equilibrium?

    asked on December 2, 2014
  10. Chemistry

    Which of the following ionic compounds has the highest melting point? Help: Lattice energy Select one: a. Cs2O b. K2O c. BeO d. SrO e. LiF f. CsI

    asked on November 10, 2014
  11. Chemistry

    In a particular redox reaction, MnO2 is oxidized to MnO4– and Cu2 is reduced to Cu . Complete and balance the equation for this reaction in acidic solution. Phases are optional. MnO2 + Cu^2+ ---> MnO4^- + Cu^+

    asked on May 4, 2014
  12. Algebra 2

    Claire has borrowed $\$5,\!000$. She plans to pay off the loan in full after two payments. She will make one payment in 3 years, then another payment in 6 years. The second payment will be exactly double the amount of the first payment. How much is the

    asked on April 4, 2017
  13. Math

    Of 30 students, 12 play football, 17 play soccer, and 5 play both, how many play neither?

    asked on March 12, 2013
  14. Statistics

    50 employees in an office wear eyeglasses. 43 have single-vision correction, and 7 wear bifocals. If two employees are selected at random from this group, what is the probability that both of them wear bifocals? What is the probability that both have

    asked on October 2, 2019
  15. Physics

    A 1200-kg frictionless roller coaster starts from rest at a height of 24 m. What is its kinetic energy when it goes over a spot that is 12 m high?

    asked on May 10, 2012
  16. math

    Three water pipes are used to fill a swimming pool. The 1st pipe alone takes 8 hours to fill the pool, the 2nd pipe alone takes 12 hours to fill the pool, and the 3rd pipe takes 24 hours to fill the pool. If all 3 pipes are opened at the same time, how

    asked on May 26, 2011
  17. algebra 2

    During the first part of a trip a canoeist travels 26 miles at a certain speed. The canoeist travels 8 miles on the second part of the trip at a speed 5 mph slower. Total time is 3 hours. What was the seed on each part of the trip

    asked on April 21, 2013
  18. geometry

    The two non-parallel sides of an isosceles trapezoid are each 7 feet long. The longer of the two bases measures 22 feet long. The sum of the base angles is 140°. a. Find the length of the diagonal. b. Find the length of the shorter base. Round your

    asked on July 26, 2017
  19. statistics

    A university dean wishes to estimate the average number of hours his part-time instructors teach per week. The standard deviation is 2.6 hours. How large a sample must be selected if he wants to be 95% confident of finding whether the true mean differs

    asked on March 30, 2011
  20. math

    Between which two consecutive integers does the radical square root of 15 lie?

    asked on September 4, 2019
  21. Physics

    The density of copper is 8.96 g cm^−3 and its molar mass is 64 g mol^−1. Calculate the mass of 1 atom of copper.

    asked on July 11, 2020
  22. Math

    Katie makes 65% of her shots from the free throw line. Can you determine how many consecutive free throws she must make in order to increase her percentage to 68%? Explain.

    asked on July 2, 2016
  23. math

    Anne wants to tie a support line from the top of a 50 foot radio tower to an anchor spot 30 feet from the tower’s base. Approximately how long will the line need to be?

    asked on June 20, 2013
  24. physics

    a small bead can slide without friction on a circular hoop that is in a vertical plane and has a radius of 0.100 m. The hoop rotates at a constant rate of 3.00 rev/s about a vertical diameter. Find the angle beta at which the bead is in vertical

    asked on October 24, 2011
  25. chemistry

    The reaction: A + 3 B = D + F was studied and the following mechanism was finally determined A + B = C (fast) C + B = D + E (slow) E + B = F (very fast) The step with largest activation energy is a. the first step b. the second step c. the third step d.

    asked on February 24, 2012
  26. Math, Please Help!!!

    a hot air balloon is rising vertically 10 ft/sec while the wind is blowing horizontally 5ft/sec. Find the speed of the balloon and the angle x that it makes with the horizontal. I know that the speed of the balloon is the square root of (10)^2 + (5)^2, but

    asked on November 10, 2011
  27. science

    Two stones are launched from the top of a tall building. One stone is thrown in a direction 30.0degree above the horizontal with a speed of 10.0m/s ; the other is thrown in a direction 30.0degree below the horizontal with the same speed. Which stone lands

    asked on September 8, 2008
  28. geometry

    the surface areas of two similar solids are 340 yd2 and 1158 yd2 the volume of the larger solids is 1712 yd3 what is the volume of the smaller solid?

    asked on May 30, 2013
  29. Math

    A biologist has determined that a particular osprey has a 70% chance of catching a fish on any given day. Carry out a simulation of 20 trials using the random number table below to find the probability that the osprey will actually catch a fish on all of

    asked on May 20, 2014
  30. chemistry

    Which of the following is not amphiprotic? a)H2O c)NH4+ e)all choices are amphiprotic b)HSO4 – d)H2PO4– need help!

    asked on March 17, 2012
  31. math

    The table shows the number of people that went to see a movie last week. Use these statements to complete the table. On Thursday, 60% of the moviegoers were male. On Friday, 35% of the moviegoers were male. On Saturday, 70% of the moviegoers were female.

    asked on January 26, 2017
  32. Chemistry

    a) Which of the following reagents would oxidize Zn to Zn2 , but not Ag to Ag ? Answers are: Co2+ Ca2+ Br2- Br2 Co or Ca b) Which of the following reagents would oxidize Ag to Ag , but not Cl– to Cl2? Answers are: Co Br- Br2 Co2+ Ca2+ or Ca

    asked on June 2, 2014
  33. Chemistry

    Calculate the total quantity of heat required to convert 25.0 g of liquid CCl4(l) from 25.0°C to gaseous CCl4 at 76.8°C (the normal boiling point for CCl4)? The specific heat of CCl4(l) is its heat of fusion is and its heat of vaporization is

    asked on April 13, 2010
  34. Math

    Peter bought 24 tickets for 490. Adult tickets =25 and student tickets = 15. How many of each type did he buy?

    asked on July 27, 2020
  35. math

    two girls caught 25 frogs. Lisa caught four times as many as Jen did. how many frogs did Jen catch

    asked on February 3, 2011
  36. chemistry

    Phosphoric acid is a triprotic acid, so H3PO4, H2PO4 -, and HPO4 2- are all acids. Which of the solutions below would have the lowest pH? 0.1 M NaH2PO4 0.1 M Na2HPO4 0.1 M Na3PO4

    asked on March 10, 2014
  37. Physics

    A woman on a bridge 75.0m high sees a raft floating at a constant speed on the river below. She drops a stone from rest in an attempt to hit the raft. The stone is released when the raft has 7.00m more to travel before passing under the bridge. The stone

    asked on November 19, 2013
  38. physics

    two objects are thrown from the top edge of a cliff with a speed of 10 m/s. one object is thrown straight down and the other straight up. if the first object hits the ground in 4.0 second, the second hits the ground in ________ seconds after the first

    asked on August 9, 2012
  39. physics

    Net force F causes mass m1 to accelerate at rate a. A net force of 3F causes mass m2 to accelerate at rate 2a. What is the ratio of mass m1 to mass m2?

    asked on November 5, 2013
  40. Chemistry

    How do you calculate ΔSfus and ΔSvap for HCl given melting point,ΔHfus, boiling point, and ΔHvap also how do you determine the entropy change when 5.20 mol of HCl(l) freezes at atmospheric pressure.

    asked on April 25, 2014
  41. Math

    The entrance hall to the Louvre Museum in Paris is a glass and metal pyramid with a surface area of approximately 1980 square on each side . The base of the pyramid is a square that is 35.4 meters on each side. What is the slant height of the pyramid ?

    asked on April 2, 2014
  42. main ideas

    Scientists generally agree that Earth is getting warmer due to what's called the greenhouse effect. A greenhouse used for plants stays warm because sunlight and heat coming through the glass roof are mostly trapped. The heat doesn't radiate back into the

    asked on September 6, 2013
  43. Algebra

    Participants in a study of a new medication received either medication A or a placebo. Find P(placebo and improvement). You may find it helpful to make a tree diagram of the problem on a separate piece of paper. Of all those who participated in the study,

    asked on May 21, 2014
  44. geometry

    What is the most precise name for quadrilateral ABCD with vertices A(–3, 2), B(–1, 4), C(4, 4), and D(2, 2)? 1. parallelogram 2. rhombus 3. quadrilateral 4. rectangle

    asked on January 11, 2013
  45. Calculus

    for the function F(t)=ln(t^2), let f(t)=F'(t). Write the integral from a to b of f(t) dt and evaluate it with the fundamental theorem of calculus. the integral from 1 to 3 ___ dt= __

    asked on November 30, 2011
  46. Chemistry

    40.0 ml of an acetic acid of unknown concentration is titrated with 0.100 M NaOH. After 20.0 mL of the base solution has been added, the pH in the titration flask is 5.10. What was the concentration of the original acetic acid solution? (Ka(CH3COOH) = 1.8

    asked on April 10, 2011
  47. calculus

    A square-based, box-shaped shipping crate is designed to have a volume of 16ft^3. The material used to make the base costs twice as much (per ft^2) as the material in the sides, and the material used to make the top costs half as much (per ft^2) as the

    asked on November 4, 2010
  48. Chemistry

    An iron ore sample was dissolved in hydrochloric acid and the iron was obtained as Fe2+(aq). The iron solution was titrated with 38.54 mL of 0.471 M Ce4+ solution according to the balanced chemical equation below. Ce4+(aq) + Fe2+(aq) -> Ce3+(aq) +

    asked on March 11, 2009
  49. Chemistry

    What is the net ionic equation when H2SO4 is neutralized by NaOH in aqueous solution? Write the molecular equation. H2SO4 + 2NaOH ==> Na2SO4 + 2H2O Convert to ions. 2H^+ + SO4^= + 2Na^+ + 2 OH^- ==> 2Na^+ + SO4^= + 2H2O Now cancel those ions that appear on

    asked on February 17, 2007
  50. Math

    Terry bought some gum and some candy. The number of packs of chewing gum was one more than the number of mints. The number of mints was three times the number of chocolate bars. If gum cost 6 cents a pack, mints cost 3 cents each, and chocolate bars cost

    asked on June 6, 2020
  51. physics

    A force acts on a 2kg mass and gives it an acceleration of 3 m/s^2. what acceleration is produced by the same force when acting on a mass of (1) 1kg? (2) 4kg? (3) how large is the force?

    asked on October 25, 2018
  52. Calculus

    Graph the function f(x)=x+4/x Graph the secant line that passes through the points (1,5) and (8,8.5) on the same set of axes Find the number c that satisfies the conclusion of the Mean Value Theorem for f on [1,8] c= Notice that if you graph the tangent

    asked on February 8, 2015
  53. Math

    You invested $14,000 in two accounts paying 5% and 9% annual interest, respectively. If the total interest earned for the year was $820, how much was invested at each rate?

    asked on September 4, 2012
  54. Physics

    Work of 730 J is done by stirring an insulated beaker containing 80 g of water. What is the change in the temperature of the water? Please show calculation

    asked on October 19, 2011
  55. physics

    In the vertical jump, an Kobe Bryant starts from a crouch and jumps upward to reach as high as possible. Even the best athletes spend little more than 1.00 s in the air (their "hang time"). Treat Kobe as a particle and let ymax be his maximum height above

    asked on October 21, 2010
  56. Auditing

    1. Which of the following matters would an auditor most likely consider to be a significant deficiency to be communicated to the audit committee? A. Management's failure to renegotiate unfavorable long-term purchase commitments. B. Recurring operating

    asked on March 11, 2010
  57. Operations Management

    The maintenance department of a hospital uses 816 cases of liquid cleanser annually. Ordering costs are $12, carrying costs are $4 per case a year, and the new price schedule indicates that orders of less than 50 cases will cost $20 per case, 50 to 79

    asked on March 7, 2009
  58. Chemistry

    A chemist performs a series of reactions that produce binary lithium compounds. The elements include sulfur, chlorine, nitrogen, fluorine, selenium, oxygen, and iodine. The models below represent the ionic radii of compounds formed by reacting lithium with

    asked on April 13, 2020
  59. physics

    (fill in the blanks) The mass of a 300 g object is _______(a). Its weight on Earth is _______(b). An object that weighs 20N on earth has a mass on the moon equal to ________(c)

    asked on October 25, 2018
  60. geometry

    George plans to cover his circular pool for the upcoming winter season. The pool has a diameter of 20 feet and extends 12 inches beyond the edge of the pool. A rope runs along the edge of the cover to secure it in place. a. What is the area of the pool

    asked on July 26, 2017
  61. math

    In a geometric series, t1=12 and s3=372.what is the greatest possible value for t5?

    asked on June 3, 2013
  62. chemistry

    Calculate the number of carbon atoms in 0.75 L of acetone (CH3COCH3). (density = 1.3 g/mL and boiling point = 48.5 degrees Celsius)

    asked on October 31, 2010
  63. chemistry

    consider a crystallization of sulfanilamide in which 10 mL of hot 95% ethyl alcohol is added to 0.10 g of impure sulfanimide. after the solid has dissolved, the solution is cooled to room temp. and then placed into an ice-water bath. no crystals for, even

    asked on October 7, 2008
  64. Trigonometry

    The wheels of a scooter have a diameter of 4.5 inches. If the person riding the scooter is traveling down hill at 15.0 mph. what is the approximate angular speed of the wheels in radians per second

    asked on September 25, 2014
  65. Geometry :)

    Use coordinate geometry to prove that the quadrilateral formed by connecting the midpoints of a kite is a rectangle. I have no Idea how to do this problem, so if anyone could help I would be very greatfull. :)

    asked on January 15, 2013
  66. Physics

    A rock climber of mass 55 kg is hanging suspended from a rope tied to another climber of mass 65 kg on a horizontal cliff ledge. If the coefficient of kinetic friction between the climber on the ledge and the ledge is 0.45, what is the net acceleration of

    asked on July 15, 2012
  67. Economics

    Suppose that some firms in a competitive industry are earning zero economic profits, while others are experiencing losses. All else equal, in the long run, we would expect the number of firms in the industry to A. increase. B. decrease. C. remain the same.

    asked on November 29, 2011
  68. Chemistry

    Use the dilution relationship (Mi x Vi = Mf x Vf) to calculate the volume of 0.500 M NaOH needed to prepare 500 mL of .250 M NaOH. This is my work ? L Solution = 500mL x (1L/1000mL) = .500L ? mol NaOH = .500 L Solution x (0.250 M NaOH/1 L Solution) = .125

    asked on February 28, 2009
  69. math

    What set of reflections and rotations would carry rectangle ABCD onto itself? Rectangle formed by ordered pairs A at negative 4, 1, B at negative 4, 2, C at negative 1, 2, D at negative 1, 1.

    asked on September 17, 2018
  70. Data

    Bridget works part time in a shoe store. Sometimes when it is not busy, she rearranges the shoes for fun. If she takes six different pairs of shoes and rearranges them in a row, in how many ways can she rearrange them so that no two shoes match? Is the

    asked on February 14, 2017
  71. Chemistry

    The following equation represents the decomposition of a generic diatomic element in its standard state. (1/2)X2(g)--->X(g) Assume that the standard molar Gibbs energy of formation of X(g) is 5.45 kJ·mol–1 at 2000. K and –64.30 kJ·mol–1 at 3000. K.

    asked on April 25, 2014
  72. physics

    A ball of mass m = 0.75 kg is thrown straight upward with an initial speed of 8.9 m/s. Plot the gravitational potential energy of the block from its launch height, y = 0, to the height y = 5.0 m. Let U = 0 correspond to y = 0. Determine the turning point

    asked on February 13, 2011
  73. Physics B

    A car slows down from 23 m/s to rest in a distance of 85m. What is its constant acceleration? I got -6.224, but a friend was telling me it's -3.11 and that I had to divide by 2. Why is that?

    asked on September 12, 2009
  74. Chemistry

    A 0.1300 g iron ore sample was dissolved in hydrochloric acid and the iron was obtained as Fe2+(aq). The iron solution was titrated with Ce4+ solution according to the balanced chemical reaction shown below. After calculation, it was found that 0.0259 g of

    asked on March 13, 2009
  75. Geography

    The acceptance of bribes by government officials who manage natural resources is an example of... A.profit maximization. B.productivity. C.environmental regulations. D.corruption. i chose A because that was in the book and it was false

    asked on November 23, 2019
  76. math

    1. Which of the following numbers is a rational? A. 4/5 B. square root of 27 C. 4.02002000200002... D. Square root of 31 2. Which type of number is shown below? 0.313311333111... A. repeating decimal B. rational C. irrational D. terminating decimal 3.

    asked on September 21, 2016
  77. trig

    An airplane is flying in the direction 148° with an airspeed of u = 920 kilometers per hour. Because of the wind, its groundspeed and direction are v = 820 kilometers per hour and 140°, respectively (see figure). Find the direction and speed of the wind.

    asked on November 2, 2015
  78. Chemistry Buffers

    Write reactions showing how each of the following buffers would neutralize added HCl. HF and NaF Express your answer as a balanced chemical equation. Identify all of the phases in your answer. HC2H3O2 and KC2H3O2 Express your answer as a balanced chemical

    asked on November 16, 2014
  79. Math

    Webster Aquatic Center offers various levels of swimming lessons year-round. The March 2005 Monday and Wednesday evening lessons included instructions from Water Babies through Adults. The number in each classification is given in the table that follows.

    asked on July 4, 2012
  80. Trig

    From a point P on level ground, the angle of elevation of the top of a tower is 27°10'. From a point 23.0 meters closer to the tower and on the same line with P and the base of the tower, the angle of elevation of the top is 51°30'. Approximate the

    asked on June 26, 2012
  81. chemistry

    Consider the following reaction: CaCN2 + 3H2O ¨ CaCO3 + 2NH3 105.0 g CaCN2 and 78.0 g H2O are reacted. Assuming 100% efficiency, which reactant is in excess and how much is leftover? The molar mass of CaCN2 is 80.11 g/mol. The molar mass of CaCO3 is

    asked on October 31, 2010
  82. math

    Why couldn't the two elephants go swimming together?

    asked on March 17, 2009
  83. Chem

    Determine the number of moles of N atoms in 43.5 g of Mg(NO3)2. Textbook answer: 1.43 mol N My answer: 43.5 g Mg(NO3)x x (1 mol Mg(NO3)2/148.313 g Mg(NO3)2) x (2 mol N/1 mol Mg(NO3)2) = .293 Can tell me where i went wrong?

    asked on March 8, 2009
  84. Physics

    When a wheel is rotated through an angle of 35 degrees, a point on the circumference travels through an arc length of 2.5 m. When the wheel is rotated through angles of 35 rad and 35 rev, the same point travels through arc lengths of 143 m and 9.0 X 10^2

    asked on November 19, 2008
  85. Chemistry

    Consider the following chemical reaction: Cr3+(aq) + 6H2O(l) → [Cr(H2O)6]3+(aq) Would this reaction have a positive or negative entropy of formation?

    asked on November 25, 2019
  86. chemistry

    What is the mass of sodium needed to make 2 g of sodium oxide (4Na + O2 → 2Na2O)? Ar values: O = 16, Na = 23. please help I'm really struggling. also please try to explain it to the simplest form because I really don't understand.

    asked on March 14, 2019
  87. algebra

    what is the value of 11x^-3y^-1 for x = -1 and y = 2?

    asked on March 3, 2019
  88. Precalculus

    you borrow $5,000 from your parents to purchase a used car. The arrangements of the loan are such that you make payments of $250 per month toward the balance plus 1% interest on the unpaid balance from the previous month. (a) Find the first year monthly

    asked on February 6, 2018
  89. Pre Calculus

    For a vector $\bold{v}$, let $\bold{r}$ be the reflection of $\bold{v}$ over the line \[\bold{x} = t \begin{pmatrix} 2 \\ -1 \end{pmatrix}.\] [asy] unitsize(1 cm); pair O, V, R; O = (0,0); V = (3,1); R = reflect(O,(2,-1))*(V); xaxis(-2,4); yaxis(-3,1);

    asked on September 20, 2017
  90. Maths

    In class 8m, there are 27 pupils. There are twice as many boys as girls. How many boys are there?

    asked on July 3, 2016
  91. physics

    A plastic rod is rubbed against a wool shirt, thereby acquiring a charge of −4.9 µC. How many electrons are transferred from the wool shirt to the plastic rod? The elemental charge is 1.6 × 10−19 C.

    asked on March 10, 2015
  92. Math

    A fence 12ft high runs parallel to a tall building at a distance of 2ft from the building. What is the length of the shortest ladder that will reach from the ground over the fence to the wall of the building?

    asked on December 13, 2014
  93. Math

    In first gear, or low gear, an automobile's engine runs about three times as fast as the drive shaft. In second gear, the engine does not have to run as fast; usually it runs about 1.6 times faster than the drive shaft. Finally, in third, or high gear, the

    asked on June 17, 2013
  94. English II

    On a proud round cloud in a white high night. A. alliteration B. consonance C. assonance D. limerick

    asked on May 1, 2013
  95. physics 100

    Bob, who has a mass of 60 , can throw a 800 rock with a speed of 26 . The distance through which his hand moves as he accelerates the rock forward from rest until he releases it is 1.0 . a) What constant force must Bob exert on the rock to throw it with

    asked on October 13, 2012
  96. physics

    A hockey puck slides across the ice at a con- stant speed. Which of the following is true? 1. The puck is moving and thus not in equi- librium. 2. The puck can be considered neither at rest nor in equilibrium. 3. It is in equilibrium. 4. None of these 5.

    asked on October 17, 2011
  97. math

    A young man spent 1/4 of his allowance on a movie. He spent 11/18 of the remainder on after-school snacks. Then from the money remaining, he spent $3.00 on a magazine, which left him 1/24 of his original allowance to put into savings. How much of his

    asked on October 9, 2009
  98. math

    Farmer Brown had some animals. One-fourth were horses, one-half were cows, and the rest were pigs. He had 8 pigs. How many animals did he have altogether? I know you would get a common denominator for 1/4 and 1/2 which would be 4 so you would have 1/4+2/4=

    asked on February 4, 2009
  99. Geography

    is Christianity the dominant religion in North Africa? true or false? I think it's false because it's Islam right? I just want to be sure

    asked on November 23, 2019
  100. physics

    A shot putter throws the shot (mass=7.3kg) with an initial speed of 14.4 m/s at a 34.0 degree angle to the horizontal. Calculate the horizontal distance traveled by the shot if it leaves the athlete's hand at a height of 2.10m above the ground.

    asked on October 25, 2018


  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8
  9. 9
  10. 10
  11. 11
  12. 12
  13. 13
  14. 14
  15. 15
  16. 16
  17. 17
  18. 18
  19. 19
  20. 20
  21. 21