The length of pregnancies are normally distributed with a mean of 268 days and a standard deviation of 15 days.
a) Few years ago, in a letter to "Dear Abby" a wife claimed to have given birth 308 days after a brief visit from her husband, who was serving in the Navy. What is the probability that her husband was the actual father of the baby, that is, the probability of a pregnancy lasting 308 days or longer?
b) What fraction of pregnancies fall within ±10 days from the mean length of pregnancies?
c) What middle interval (of days) includes 0.95 fraction of all pregnancies? Round the days to the nearest integer.