The duration of pregnancy in humans is approximately Normally distributed with μ = 266 days and σ = 16 days. In the following questions, assume that this distribution is exact.

(a) What proportion of pregnancies last between 250 and 290 days?

(b) A post-term pregnancy is defined as one that lasts more than 294 days. What proportion of pregnancies are post-term?

(c) What durations give the quartiles of the distribution of human pregnancy durations?