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: when 242 is divided by a certain divisor the remainder obtained is 15. when 698 is divided by the same divisor the remainder obtained is 27. however, when the sum of the two numbers 242 and 698 is divided by the divisor, the remainder obtained is 5. what is the value of the divisor ?
Options: a. 11, b. 17, c. 13, d. 23, e. 37
Example Output: e

Example Input: Problem: a man can row upstream at 25 kmph and downstream at 55 kmph, and then find the speed of the man in still water ?
Options: a. 65, b. 40, c. 30, d. 78, e. 38
Example Output: b

Example Input: Problem: in an examination, a student scores 4 marks for every correct answer and loses 1 mark for every wrong answer. if he attempts all 200 questions and secures 240 marks, the number of questions he attempts incorrectly, is :
Options: a. 135, b. 200, c. 140, d. 112, e. 48
Example Output:
d