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: in a factory, an average of 60 tv ' s are produced per day for the fist 25 days of the months. a few workers fell ill for the next 5 days reducing the daily avg for the month to 58 sets / day. the average production per day for day last 5 days is ?
Options: a. 20, b. 36, c. 48, d. 50, e. 59

Ex Output:
c

Ex Input:
Problem: in what ratio must a grocer mix two varieties of pulses costing rs. 15 and rs. 20 per kg respectively so as to get a mixture worth rs. 16.50 per kg ?
Options: a. 3: 7, b. 5: 7, c. 7: 3, d. 7: 5, e. none

Ex Output:
c

Ex Input:
Problem: a car runs at the speed of 25 km per hour when not serviced and runs at 75 kmph when serviced. after servicing the car covers a certain distance in 5 hours. how much time will the car take to cover the same distance when not serviced ?
Options: a. 8 hours, b. 16 hours, c. 15 hours, d. 7 hours, e. none

Ex Output:
d