z test or T test

Q#2 A manufacturing company consists of two departments producing identical products. It is suspected that the hourly output of two departments are different. Two samples of production hour are selected from both departments and the following data obtained Department 1 Department 2 Sample size 64 49 Sample mean 100 90 Population variance 256 196 Test the hypothesis that mean hourly output of department 2 is greater than department 1 Also test the hypothesis that mean hourly output of department 1 is greater than department 2