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: if each participant of a chess tournament plays exactly one game with each of the remaining participants, then 276 games will be played during the tournament. find the number of participants.
Options: a. 20, b. 22, c. 24, d. 26, e. 28

Ex Output:
c


Ex Input:
Problem: at what price must an article costing rs. 47.50 be marked in order that after deducting 7 % from the list price. it may be sold at a profit of 25 % on the cost price ?
Options: a. 63.84, b. 62.6, c. 62.1, d. 62.7, e. 62.2

Ex Output:
a


Ex Input:
Problem: two trains of equal are running on parallel lines in the same direction at 48 km / hr and 36 km / hr. the faster train passes the slower train in 36 sec. the length of each train is ?
Options: a. 60 m, b. 72 m, c. 80 m, d. 82 m, e. 84 m

Ex Output:

a