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 store reported total sales of $ 460 million for february of this year. if the total sales for the same month last year was $ 320 million, approximately what was the percent increase in sales ?
Options: a. 2 %, b. 17 %, c. 44 %, d. 65 %, e. 83 %

Ex Output:
c

Ex Input:
Problem: what will be the percentage increase in the area of the cube ' s surface if each of the cube ' s edges grows by 40 % ?
Options: a. 95 %, b. 90 %, c. 85 %, d. 96 %, e. 25 %

Ex Output:
d

Ex Input:
Problem: a student got 70 % in one subject, 80 % in other. to get overall 75 % how much he should get in third subject.
Options: a. 65 %, b. 75 %, c. 85 %, d. 95 %, e. 88 %

Ex Output:
b