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 32 ! + 50 ! + 4 ! + 4 ! ?
Options: a. 0, b. 2, c. 4, d. 6, e. 8

Ex Output:
e


Ex Input:
Problem: barbata invests $ 2200 in the national bank at 5 %. how much additional money must she invest at 8 % so that the total annual income will be equal to 6 % of her entire investment ?
Options: a. 1100, b. 3000, c. 1000, d. 3600, e. 2400

Ex Output:
a


Ex Input:
Problem: an urn contains 5 red, 6 blue and 8 green balls. 3 balls are randomly selected from the urn, find the probability that the drawn ball are blue ?
Options: a. 20 / 969, b. 20 / 875, c. 21 / 876, d. 3 / 512, e. 2 / 9

Ex Output:

a