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: find the simple interest on rs. 72,000 at 16 2 / 3 % per year for 9 months.
Options: a. 7500, b. 6500, c. 9000, d. 9500, e. none of them

Ex Output:
c


Ex Input:
Problem: if a is a positive integer, and if the units digit of a ^ 2 is 4 and the units digit of ( a + 1 ) ^ 2 is 1, what is the units digit of ( a + 2 ) ^ 2 ?
Options: a. 0, b. 2, c. 4, d. 6, e. 8

Ex Output:

a