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: what sum of money will produce rs. 80 as simple interest in 4 years at 3 1 / 2 percent ?
Options: a. 263, b. 571.4, c. 367, d. 368, e. 339

Ex Output:
b


Ex Input:
Problem: in traveling from a dormitory to a certain city, a student went 1 / 3 of the way by foot, 3 / 5 of the way by bus, and the remaining 2 kilometers by car. what is the distance, in kilometers, from the dormitory to the city ?
Options: a. 30, b. 45, c. 60, d. 90, e. 120

Ex Output:
a


Ex Input:
Problem: a train 50 m long takes 6 sec to cross a man walking at 5 kmph in a direction opposite to that of the train. find the speed of the train ?
Options: a. 15 kmph, b. 25 kmph, c. 35 kmph, d. 45 kmph, e. 55 kmph

Ex Output:

b