Suppose that a sample of 15 randomly chosen people were put on a special weight loss diet. The amount of weight lost, in pounds, follows an unknown distribution with mean equal to 12 pounds and...

Suppose that a sample of 15 randomly chosen people were put on a special weight loss diet.  The amount of weight lost, in pounds, follows an unknown distribution with mean equal to 12 pounds and standard deviation equal to 3 pounds. Assume that the distribution for the weight loss is normal.

a.  Find the probability that the mean amount of weight lost by 15 people is no more than 14 pounds.