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 shopkeeper buys mangoes at the rate of 5 a rupee and sells them at 2 a rupee. find his net profit or loss percent ?
Options: a. 34 %, b. 30 %, c. 50 %, d. 150 %, e. 33 %
Example Output: d

Example Input: Problem: a mixture of 70 litres of milk and water contains 10 % water. how many litres of water should be added to the mixture so that the mixture contains 12 1 / 2 % water ?
Options: a. 2, b. 8, c. 6, d. 3, e. 4
Example Output: a

Example Input: Problem: in february wilson ’ s earnings were 40 percent of his family ’ s total income. in march wilson earned 25 percent less than in february. if the rest of his family ’ s income was the same in both months, then, in march, wilson ’ s earnings were approximately what percent q of his family ’ s total income ?
Options: a. 15 %, b. 17 %, c. 24 %, d. 30 %, e. 33 %
Example Output:
e