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.

Ex Input:
Problem: there are 750 male and female participants in a meeting. half the female participants and one - quarterof the male participants are democrats. one - third of all the participants are democrats. how many of the democrats are female ?
Options: a. 75, b. 100, c. 125, d. 175, e. 225

Ex Output:
c

Ex Input:
Problem: a man swims downstream 36 km and upstream 18 km taking 3 hours each time, what is the speed of the man in still water ?
Options: a. 7, b. 8, c. 9, d. 2, e. 4

Ex Output:
c

Ex Input:
Problem: the difference between simple interest and compound interest on rs. 1400 for one year at 20 % per annum reckoned half - yearly is :
Options: a. $ 185.63, b. $ 852.36, c. $ 875.5, d. $ 989.9, e. $ 875.8

Ex Output:
d