Researchers studying the effects of a new diet found that the weight loss over a one-month period by those on the diet was normally distributed with

Researchers studying the effects of a new diet found that the weight loss over a one-month period by those on the diet was normally distributed with a mean of 9 pounds and a standard deviation of 3 pounds. If a dieter is selected at random, what is the probability that the dieter lost at most 7.5 pounds?