A teacher gave the same test to three history classes: A, B, and C. The average
(arithmetic mean) scores for the three classes were 65, 80, and 77, respectively. The ratio
of the numbers of students in each class who took the test was 4 to 6 to 5, respectively.
What was the average score for the three classes combined?
A. 74
B. 75
C. 76
D. 77
E. 78

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