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: 18.05 ã — 0.001 = ?
Options: a. 0.1805, b. 0.01805, c. 1.805, d. 0.001805, e. none of these

Ex Output:
b


Ex Input:
Problem: if each participant of a chess tournament plays exactly one game with each of the remaining participants, then 276 games will be played during the tournament. find the number of participants.
Options: a. 20, b. 22, c. 24, d. 26, e. 28

Ex Output:
c


Ex Input:
Problem: if pintu is coded as 79523 in a certain code language, how would you code dumbo in the same language ?
Options: a. 43426, b. 14236, c. 13436, d. 14263, e. 15263

Ex Output:

a