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: a cricket player whose bowling average was 21.5 runs per wicket, takes 5 wicket for 52 runs in a match. due to this his average decreases by 0.5. what will be the number of wickets taken by him till the last match ?
Options: a. 64, b. 72, c. 111, d. 721, e. 108
Example Output: c

Example Input: Problem: a train 100 meters long completely crosses a 300 meters long bridge in 36 seconds. what is the speed of the train is ?
Options: a. 32 kmph, b. 76 kmph, c. 34 kmph, d. 43 kmph, e. 40 kmph
Example Output: e

Example Input: Problem: there is a square with sides of 12. what is the circumference of the biggest circle that can be cut out of this square ?
Options: ['a. 75.4', 'b. 31.42', 'c. 36', 'd. 18.85', 'e. 37.7']
Example Output:
e