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 12 red marbles. if someone were to remove 2 marbles from the bag, one at a time, and replace the first marble after it was removed, the probability that neither marble would be red is 25 / 36. how many marbles are in the bag ?
Options: a. 24, b. 48, c. 60, d. 72, e. 84
Example Output: b

Example Input: Problem: the average runs scored by a batsman in 20 matches is 40. in the next 10 matches the batsman scored an average of 30 runs. find his average in all the 30 matches ?
Options: a. 31, b. 36.67, c. 88, d. 13, e. 12
Example Output: b

Example Input: Problem: the milk level in a rectangular box measuring 58 feet by 25 feet is to be lowered by 6 inches. how many gallons of milk must be removed ? ( 1 cu ft = 7.5 gallons )
Options: a. 100, b. 250, c. 750, d. 5437.5, e. 5635.5
Example Output:
d