a.A manufacturer knows that their items have a normally distributed length, with a mean of 15.9 inches, and standard deviation of 2.3 inches.

If 25 items are chosen at random, what is the probability that their mean length is less than 14.8 inches?

b.The lengths of pregnancies in a small rural village are normally distributed with a mean of 260 days and a standard deviation of 16 days. A distribution of values is normal with a mean of 260 and a standard deviation of 16.

What percentage of pregnancies last fewer than 298 days?

P(X< 298 days)