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 11 10 prime numbers which are odd is ?
Options: a. 17.72, b. 18.52, c. 19.63, d. 16.53, e. 15.63
Example Output: a

Example Input: Problem: the average score of a cricketer in 2 matches is 30 and in other 3 matches is 40. then find the average score in all the 5 matches ?
Options: a. 25, b. 27, c. 30, d. 35, e. 36
Example Output: e

Example Input: Problem: raja spends 35 % of his monthly income on household items, 20 % of his monthly income on buying cloths, 5 % of his monthly income on medicines and saves the remaining amount which is rs. 15000. find his monthly income.
Options: a. rs. 40000, b. rs. 36000, c. rs. 37500, d. rs. 45000, e. none of these
Example Output:
c