Please help with this hw question

(9) The length of human pregnancy is normally distributed with mean 266 days and standard deviation of 16 days. (a) (9pts) What is the probability that a random sample of 49 pregnancies has a mean gestation period of 260 or more? Draw a good diagram and show the z-scores. (b) (9pts) What is the probability that a random sample of 64 pregnancies has a mean gestation period between 260 and 275? Draw a good diagram and show the z-scores