The lengths of human pregnancies are approximately normally distributed, with mean = 266 days and standard

Question:

The lengths of human pregnancies are approximately normally distributed, with mean µ = 266 days and standard deviation σ = 16 days.
(a) What proportion of pregnancies lasts more than 270 days?
(b) What proportion of pregnancies lasts less than 250 days?
(c) What proportion of pregnancies lasts between 240 and 280 days?
(d) What is the probability that a randomly selected pregnancy lasts more than 280 days?
(e) What is the probability that a randomly selected pregnancy lasts no more than 245 days?
(f ) A “very preterm” baby is one whose gestation period is less than 224 days. Are very preterm babies unusual?