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Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

Problem: a school has 4 section of chemistry in class x having 40, 35, 45 and 42 students. the mean marks obtained in chemistry test are 50, 60, 55 and 45 respectively for the 4 sections. determine the overall average of marks per student.
Options: a. 50.25, b. 52.25, c. 51.25, d. 53.25, e. none of the above
Output:
b