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: it is only in the second option we find the sentence a in continuation with the opening sentence d. sentence a alone explains, why the fear has such enormous effect on the human beings.
Options: a. 28, b. 99, c. 728, d. 27, e. 271

Ex Output:
b


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: an art gallery has only paintings and sculptures. currently, 1 / 3 of the pieces of art are displayed, and 1 / 6 of the pieces on display are sculptures. if 1 / 3 of the pieces not on display are paintings, and 800 sculptures are not on display, how many pieces of art does the gallery have ?
Options: a. 360, b. 1800, c. 540, d. 640, e. 720

Ex Output:

b