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.

Input: Consider Input: Problem: the price of a book is increased from $ 300 to $ 390. what is the % of increase in its price ?
Options: a. 10 %, b. 20 %, c. 30 %, d. 35 %, e. 45 %

Output: c


Input: Consider Input: Problem: if the simple interest on a certain amount in at 4 % rate 5 years amounted to rs. 2240 less than the principal. what was the principal ?
Options: a. 1500, b. 2500, c. 2507, d. 2800, e. 11500

Output: d


Input: Consider Input: Problem: if the average ( arithmetic mean ) of the 4 numbers 3, 16, 33, and ( n + 1 ) is 20, then n =
Options: a. 19, b. 20, c. 21, d. 27, e. 29


Output: d