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 can give b 100 meters start and c 200 meters start in a kilometer race. how much start can b give c in a kilometer race ?
Options: a. 111.12 m, b. 221.12 m, c. 271.12 m, d. 611.12 m, e. 191.12 m

Ex Output:
a


Ex Input:
Problem: two positive integers differ by 4, and sum of their reciprocals is 2. then one of the numbers is
Options: a. a. 3, b. 2, c. c. 5, d. d. 21, e. e. 28

Ex Output:
b


Ex Input:
Problem: the average age of 20 students of a class is 20 years. out of these, the average age of 9 students is 11 years and that of the other 10 students is 24 years. the age of the 20 th student is ?
Options: a. 65, b. 61, c. 59, d. 63, e. 64

Ex Output:

b