12 A study is conducted of the geographic distribution of the residences of the employees at a large factory. in order to determine the suitability of initiating busing to that factory. One variable considered is the distance the employee lives from the factory For a randomi sample of 100 employees, the mean distance is 6.3 miles and the standard deviation is 4.0.

a) Find and interpret a 90% confidence interval for the mcan residential distance from the factors of all employees.

b) About how large a sample would have been adequate if we merely needed to estimate the incan to within 1.0. with 90% confidence?