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 is the units digit of ( 3 ^ 13 ) ( 4 ^ 13 ) ?
Options: a. 2, b. 4, c. 6, d. 7, e. 8

Ex Output:
a


Ex Input:
Problem: during a given week a programmer spends 1 / 4 of his time preparing flow chart, 3 / 8 of his time coding and the rest of the time in debugging the programs. if he works 48 hours during the week, how many hours did he spend debugging the program.
Options: a. 15 hrs, b. 16 hrs, c. 18 hrs, d. 19 hrs, e. 17 hrs

Ex Output:
c


Ex Input:
Problem: in a class, 5 people like baseball and football, 2 people only like baseball, 3 people only like football, and 6 people like neither. how many people are in the class ?
Options: ['a. 10', 'b. 14', 'c. 16', 'd. 20', 'e. 22']

Ex Output:

c