The lengths of pregnancies are normally distributed with a mean of 266 days and a standard deviation of 15 days. a. Find the probability of a pregnancy lasting 309 days or longer. b. If the length of pregnancy is in the lowest 4%, then the baby is premature. Find the length that separates premature babies from those who are not premature. Click to view page 1 of the table. Click to View page 2 of the table. a. The probability that a pregnancy will last 309 days or longer is D. (Round to four decimal places as needed.)