The lengths of a particular animal's pregnancies are approximately normally distributed, with mean = 255 days and standard deviation = 8 days. (a) What proportion of pregnancies lasts more than 265 days? (b) What proportion of pregnancies lasts between 251 and 261 days? (c) What is the probability that a randomly selected pregnancy lasts no more than 239 days? (d) A "very preterm" baby is one whose gestation period is less than 243 days. Are very preterm babies unusual? (a) The proportion of pregnancies that last more than 265 days is (Round to four decimal places as needed.) .