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: calculate the share of z, if rs. 3720 is divided among x, y and z in the ratio 7: 8: 11 ?
Options: a. 1564.1, b. 1214.1, c. 1574.1, d. 1271.1, e. 1044.1

Ex Output:
c

Ex Input:
Problem: two pipes a and b can fill a tank in 36 hours and 46 hours respectively. if both the pipes are opened simultaneously, how much time will be taken to fill the tank ?
Options: a. 20.195 hrs, b. 21.195 hrs, c. 22.195 hrs, d. 23.195 hrs, e. 20.495 hrs

Ex Output:
a

Ex Input:
Problem: in one hour, a boat goes 11 km along the stream and 5 km against the stream. the speed of the boat in still water is :
Options: a. 3, b. 5, c. 8, d. 9, e. 10

Ex Output:
c