Instructions: 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.
Input: Problem: a library has an average of 510 visitors on sundays and 240 on other day. the average number of visitors in a month of 50 days starting with sunday is
Options: a. 280, b. 285, c. 171, d. 295, e. 275
Output:
c