The University of Missouri-St. Louis gave a validation test to entering students who had taken calculus in high school. There are 121 students overall, 28 of which received college credit for the calculus they took in high school and 93 of which did not receive college credit. The group of 93 students receiving no college credit had a mean score of 4.17 on the validation test with a sample standard deviation of 3.7 ( p s = P(xi − X¯) 2/(93 − 1) = 3.7). For the 28 students who received credit from a high school dual-enrollment class, the mean score was 4.61 with a sample standard deviation of 4.28. (a) Find a 95% confidence int