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 bag contains 10 green and 8 white balls. if two balls are drawn simultaneously, the probability that both are of the same colour is
Options: a. 8 / 15, b. 21 / 44, c. 3 / 5, d. 11 / 15, e. 7 / 15
Example Output: b

Example Input: Problem: the smallest number which when diminished by 2, is divisible by 12, 16, 18, 21 and 28 is
Options: a. 1008, b. 1010, c. 1022, d. 1032, e. 1043
Example Output: b

Example Input: Problem: a student completes a 3 part exam as follows. the student completes sections a in 4 minutes and takes an equal time to complete the two remaining sections. what is the ratio of time spent on section c to section a if the total duration is 1 hour ?
Options: a. 10: 3, b. 9: 2, c. 7: 1, d. 8: 3, e. 11: 2
Example Output:
c