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.

Example Input: Problem: the average of first five multiples of 7 is :
Options: a. 9, b. 16, c. 15, d. 8, e. 21
Example Output: e

Example Input: Problem: ramesh purchased a refrigerator for rs. 12500 after getting a discount of 20 % on the labelled price. he spent rs. 125 on transport and rs. 250 on installation. at what price should it be sold so that the profit earned would be 18 % if no discount was offered ?
Options: a. 17608, b. 17606, c. 17604, d. 17600, e. 18880
Example Output: e

Example Input: Problem: if a * b * c = ( √ ( a + 2 ) ( b + 3 ) ) / ( c + 1 ), find the value of 6 * 15 * 1.
Options: a. 8, b. 5, c. 2, d. 3, e. 4
Example Output:
c