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.
--------
Question: Problem: find the maximum value of the function f ( x ) = x − 5 if x is a number between - 5 and 13.
Options: a. 6, b. 7, c. 8, d. 9, e. none

Answer: c


Question: Problem: the ` ` racing magic ' ' takes 120 seconds to circle the racing track once. the ` ` charging bull ' ' makes 40 rounds of the track in an hour. if they left the starting point together, how many minutes will it take for them to meet at the starting point for the second time ?
Options: a. 3, b. 6, c. 9, d. 12, e. 15

Answer: d


Question: Problem: average of 5 numbers is 20, and the sum of 3 of the numbers is 48, what is the average of the other 2 numbers ?
Options: a. 24, b. 34, c. 29, d. 35, e. 26

Answer:
e