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: ravi purchased a refrigerator and a mobile phone for rs. 15000 and rs. 8000 respectively. he sold the refrigerator at a loss of 5 percent and the mobile phone at a profit of 10 percent. overall he make a.
Options: a. 50, b. 288, c. 27, d. 200, e. 881

Ex Output:
a

Ex Input:
Problem: 108 a 108 + 92 a 92 = ?
Options: a. 20120, b. 11500, c. 20128, d. 20660, e. 20228

Ex Output:
c

Ex Input:
Problem: circular gears p and q start rotating at the same time at constant speeds. gear p makes 10 revolutions per minute and gear q makes 40 revolutions per minute. how many seconds after the gears start rotating will gear q have made exactly 45 more revolutions than gear p ?
Options: a. 45, b. 80, c. 90, d. 100, e. 120

Ex Output:
c