A survey is being planned to determine the mean amount of time corporation executives watch television. A pilot survey indicated that the mean time per week is 20 hours, with a standard deviation of 5.5 hours. It is desired to estimate the mean viewing time within two-quarter hour. The 90 percent level of confidence is to be used.
(a) How many executives should be survyed? Number of executives ______. (Round up your answer to the next whole number.)