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: if the population of a certain country increases at the rate of one person every 15 seconds, by how many persons does the population increase in 25 minutes ?
Options: a. 80, b. 100, c. 150, d. 240, e. 300
Example Output: b

Example Input: Problem: a merchant marks his goods up by 30 % and then offers a discount of 10 % on the marked price. what % profit does the merchant make after the discount ?
Options: a. 17 %, b. 25 %, c. 69 %, d. 31 %, e. 19 %
Example Output: a

Example Input: Problem: a courtyard is 25 meter long and 16 meter board is to be paved with bricks of dimensions 20 cm by 10 cm. the total number of bricks required is :
Options: a. 16000, b. 18000, c. 20000, d. 22000, e. none of these
Example Output:
c