The lengths of a particular animal's pregnancies are approximately normally distributed, with mean u = 268 days and standard deviation 0: 12 days. (a) What proportion of pregnancies lasts more than 271 days? (b) What proportion of pregnancies lasts between 259 and 274 days? > (c) What is the probability that a randomly selected pregnancy lasts no more than 253 days? (d) A \"very preterm" baby is one whose gestation period is less than 241 days. Are very preterm babies unusual? - ' E>~