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.

Ex Input:
Problem: cathy and jim begin running at the same time and they start at the same place on a straight path. cathy runs at 10 miles per hour, and jim runs at 6 miles per hour. after 18 minutes, cathy stops to stretch. if it takes cathy 27 minutes to stretch and jim continues to run during this time, how many minutes will it take cathy to catch up to jim ?
Options: a. 20.5, b. 21.5, c. 22.5, d. 23.5, e. 24.5

Ex Output:
c

Ex Input:
Problem: when a certain number x is divided by 61, the remainder is 24. what is the remainder when x is divided by 5 ?
Options: a. 2, b. 3, c. 4, d. 5, e. 6

Ex Output:
c

Ex Input:
Problem: if 70 % of a number is equal to two - third of another number, what is the ratio of first number to the second number ?
Options: a. 5: 7, b. 18: 23, c. 17: 19, d. 20: 21, e. 2: 3

Ex Output:
d