Definition: 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: two clocks are set correctly at 1 0 ' clock in the afternoon. one keeps correct time. the other gains 5 seconds per minute. that evening, when the fast clock shows 6: 20, what does the correct clock show ?
Options: a. 4.0, b. 5.0, c. 6.0, d. 7.2, e. 3.5
Output:
c