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 man sitting in a train which is traveling at 36 kmph observes that a goods train, traveling in opposite direction, takes 10 seconds to pass him. if the goods train is 240 m long, find its speed
Options: a. 50 kmph, b. 56 kmph, c. 58 kmph, d. 62 kmph, e. 72 kmph

Ex Output:
a


Ex Input:
Problem: 54671 - 14456 - 31466 = ?
Options: a. 2449, b. 5449, c. 8749, d. 8449, e. 6468

Ex Output:
c


Ex Input:
Problem: in a certain animal population, for each of the first 3 months of life, the probability that an animal will die during that month is 1 / 4. for a group of 200 newborn members of the population, approximately how many would be expected to survive the first 3 months of life ?
Options: a. 40, b. 46, c. 52, d. 62, e. 85

Ex Output:

e