The lengths of pregnancies are normally distributed with a mean of 270 days and a standard deviation
of 15 days.
a. In a letter to an advice column, a wife claimed to have given birth 309 days after a brief visit from
her husband, who was working in another country. Find the probability of a pregnancy lasting 309
days or longer. What does the result suggest?
b. If the length of pregnancy is in the lowest 3%, then the baby is premature. Find the length that
separates premature babies from those who are not considered premature.