The length of human pregnancies from conception to birth varies according to a normal distribution with mean 268 days and a standard deviation 19 days.
A. If one birth is selected at random, then find the probability the pregnancy lasted no more than 250 days
B. If 1000 births are randomly selected then how many of the pregnancies would be expected to last no more than 250 days
C. Atleast how many days do the longest 25 percent of pregnancies last?