A study of the career paths of hotel general managers sent questionnaires to a random sample of 97 hotels belonging to major U.S. hotel chains. The average time these 97 general managers had spent with their current company was 12.75 years. (Take it as known that the standard deviation of time with the company for all general managers is 1.8 years.)

(a) Find the bound for an 80% confidence interval to estimate the mean time a general manager had spent with their current company:years

(b) Find the bound for a 99% confidence interval to estimate the mean time a general manager had spent with their current company:years

(c) In general, increasing the confidence levelthe bound of the confidence interval. (Enter: ''DECREASES'', ''DOES NOT CHANGE'' or ''INCREASES'', without the quotes.)