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: what percent is 6 gm of 1 kg ?
Options: a. 1.5 %, b. 0.5 %, c. 0.6 %, d. 3.5 %, e. 4 %
Example Output: c

Example Input: Problem: find the area of a parallelogram with base 10 cm and height 20 cm.
Options: a. 200, b. 384, c. 200, d. 244, e. 242
Example Output: c

Example Input: Problem: find the area of trapezium whose parallel sides are 28 cm and 18 cm long, and the distance between them is 15 cm.
Options: a. 227, b. 299, c. 345, d. 161, e. 212
Example Output:
c