A professor teaches two statistics classes. The morning class has 25 students and their average on the first test was 82. The evening class has 15 students and their average on the same test was 74. What is the average on this test if the professor combines the scores for both classes?
a) 76
b) 78
c) 79
d) 80
e) The average cannot be calculated since individual scores of each student are not available.