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.

Example Input: Problem: if each participant of a chess tournament plays exactly one game with each of the remaining participants, then 276 games will be played during the tournament. find the number of participants.
Options: a. 20, b. 22, c. 24, d. 26, e. 28
Example Output: c

Example Input: Problem: what is the smallest integer that is multiple of 5, 711
Options: a. a. 70, b. b. 35, c. c. 385, d. d. 280, e. e. 140
Example Output: c

Example Input: Problem: the sum of three consecutive even numbers is 366. find the middle number of the three ?
Options: a. 111, b. 123, c. 122, d. 152, e. 142
Example Output:
c