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: how many multiples of 4 are there between 12 and 104, inclusive ?
Options: a. 21, b. 22, c. 23, d. 24, e. 25

Ex Output:
d


Ex Input:
Problem: if john makes a contribution to a charity fund at school, the average contribution size will increase by 50 % reaching $ 75 per person. if there were 1 other contributions made before john ' s, what is the size of his donation ?
Options: a. $ 100, b. $ 150, c. $ 200, d. $ 250, e. $ 450

Ex Output:
a


Ex Input:
Problem: a batsman in his 12 th inning makes a score of 60 and their by increasing his average by 4. what is his average after the 12 th inning ?
Options: a. 12, b. 16, c. 20, d. 24, e. 28

Ex Output:

b