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: at what rate percent per annum will a sum of money double in 6 years.
Options: a. 12.5 %, b. 13.5 %, c. 11.5 %, d. 14.5 %, e. 16.6 %

Output: e

Input: Consider Input: Problem: the area of a triangle is with base 18 m and height 6 m ?
Options: a. 88 m 2, b. 10 m 2, c. 66 m 2, d. 54 m 2, e. 31 m 2

Output: d

Input: Consider Input: Problem: if the difference between the length and breadth of a rectangle is 23 m and its perimeter is 266 m, what is its area ?
Options: a. 4290, b. 2535, c. 2530, d. 2515, e. 2520
Output: a