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: what is the compound interest paid on a sum of rs. 3000 for the period of 2 years at 10 % per annum.
Options: a. 630, b. 620, c. 610, d. 600, e. none of these

Output: a

Input: Consider Input: Problem: by selling 15 pencils for a rupee a man loses 20 %. how many for a rupee should he sell in order to gain 20 % ?
Options: a. 8, b. 7, c. 6, d. 4, e. 10

Output: e

Input: Consider Input: Problem: a cube is painted red on all faces. it is then cut into 27 equal smaller cubes. how many h cubes are painted on only 2 faces ?
Options: a. 12, b. 8, c. 6, d. 10, e. 16
Output: a