The lengths of specific animal's pregnancies are approximately normally distributed , with mean u = 262 days and standard deviation o = 12 days.
a) What proportion of pregnancies last more than 280 days?
b) What proportion of pregnancies last between 253 and 271 days?
c) What is the probability that randomly selected pregnancy last no more than 241 days?
d) A "very preterm" baby is one whose gestation period is less than 232 days. Are very preterm babies unusual?
Round to four decimals for all problems.