7. (10 marks) Suppose the population r is normally distributed. Specify the appropriate hypothesis test and determine the appropriate critical z or t point(s) for each of the following tests concerning the population mean /: (a) (2 marks) upper-tailed test: o = 0.025, n = 25, 0 = 3.0. (b) (3 marks) lower-tailed test: a = 0.05, n = 30, s = 9.0. (c) (3 marks) two-tailed test: a = 0.02, n = 51, s = 6.5. (d) (2 marks) two-tailed test: o = 0.10, n = 36,o = 3.8