statistik
posted by mira .
the average starting salary of this yaer's graduates of a large university (LU)is $25000 with a standard deviation of $5000.futhermore,it is known that the starting salaries are normally distributed.
a)what is the probability that a randomly selected LU graduate will have a starting of at least $31000?
b)individuals with starting salaries of less than $12200 receive a low income tax break.what percentage of the graduates will receive the tax break?
C)what are the minimum and the maximum starting salaries of the middle 95% of the LU graduates?
d)if 68 of the recent gradutes have salaries of at least $35600 , how many students graduated this year from this university>

a, b) Z = (scoremean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportions related to the Z scores.
c) Use same table to find percent (47.5%) between Z score and mean. Insert Z score in above equation and solve.
d) Find Z score, use table to get %. That % of total = 68.