Two random samples were selected independently from populations having normal distributions. The statistics given below were extracted from the samples. Complete parts a through c. X1 = 40.1 X7 = 28.8 a. If of =5 and 62 = 4 and the sample sizes are n, =60 and n2 = 60, construct a 90% confidence interval for the difference between the two population means. The confidence interval is |= (H1 - 12) = (Round to two decimal places as needed.) b. If 61 = 62, S, =5, and s2 = 4, and the sample sizes are n, = 20 and ny = 20, construct a 90% confidence interval for the difference between the two population means. The confidence interval is |= (H1 - 12) = (Round to two decimal places as needed.) C. If 61 #62, S, =5, and s2 = 4, and the sample sizes are n, = 20 and n2 = 20, construct a 90% confidence interval for the difference between the two population means. The confidence interval is|= (H1 - 12) = (Round to two decimal places as needed.)