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: a cyclist bikes x distance at 8 miles per hour and returns over the same path at 10 miles per hour. what is the cyclist ' s average rate for the round trip in miles per hour ?
Options: a. 8.1, b. 8.9, c. 8.6, d. 8.3, e. 9.0

Ex Output:
b


Ex Input:
Problem: three 6 faced dice are thrown together. the probability that exactly two dice show the same number on them is
Options: a. 5 / 15, b. 5 / 12, c. 5 / 19, d. 5 / 12, e. 5 / 11

Ex Output:
b


Ex Input:
Problem: 1.5, 2.5, 4.5, 7.5, 11.5, (.... )
Options: a. 16.5, b. 15.5, c. 14.5, d. 17.5, e. 17

Ex Output:

a