Data from a National Health Survey show that men's average weight is normally distributed with a mean of 170 pounds and a standard deviation of 30 pounds.
a. If a man is chosen at random, what is the probability that his weight is greater than 180 pounds?
b. If 100 men are randomly selected, what is the probability that their mean weight is greater than 180 pounds?
c. What is the probability that mean weight of the 100 men is less than 160 pounds?