Assume that the standard deviation of daily internet usage time is 1 hour for all university students in Taiwan. Given a random sample of n such students:
(a) When n = 16 and the sample mean of daily internet usage time is 4.2 hours. Test whether the real usage time exceeds 4 hours.
(b) When n = 49 and the sample mean of internet daily usage time is 3.5 hours. Test whether the real usage time exceeds 4 hours.