State the null hypothesis, Ho, and the alternative hypothesis, Ha, that would be used for a hypothesis test for each of the following statements:
a. The mean age of the youths who hang out at the mall is less than 16 years.
b. The mean height of professional basketball players is greater than 6 ft 6 in.
c. The mean elevation drop for ski trails at eastern ski centers is at least 285 feet.
d. The mean diameter of the rivets is no more than 0.375 inch.
e. The mean cholesterol level of male college students is different from 200 mg/dL.