20. In January 2003, the American worker spent an average of 77 hours logged on to the Internet while at work (CNBC, March 15, 2003). Assume the population mean is 77 hours, the times are normally distributed, and that the standard deviation is 20 hours.

a. What is the probability that in January 2003 a randomly selected worker spent fewer than 50 hours logged on to the Internet?

b. What percentage of workers spent more than 100 hours in January 2003 logged on to the Internet?

c. A person is classified as a heavy user if he or she is in the upper 20% of usage. In January 2003, how many hours did a worker have to be logged on to the Internet to be considered a heavy user?