Mars University wants to estimate the total number of calls placed by its employees during one day. The university consis13 of N=1 departments and the ith department has M5 employees, 1 = 1, 2, - - - . N. A srs of n=5 departments is selected. Then a subsample of 20% of employees is taken from each selected department. The following data is obtained Dept. no. No. of empl. No. of empl. In the subsample No of calls made 1 20 4 4 5 6 3 2 30 6 2 4 7 5 3 6 3 15 3 6 7' 6 4- 25 5 3 6 4- 5 2 5 35 7 5 6 4 7 3 2 1 Assume that at Mars University, the total number of employees is 1500. a) Estimate the average number of phone calls an employee makes per day. b) Set up an approximate 95% CI for the true average number of calls made per employee