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: if 20 typists can type 50 letters in 30 minutes, then how many letters will 40 typists working at the same rate complete in 1 hour ?
Options: a. 400, b. 500, c. 350, d. 250, e. 200
Example Output: a

Example Input: Problem: a company produces 50000 bottles of water everyday. if a case can hold 25 bottles of water. how many cases are required by the company to hold its one day production
Options: a. 2000, b. 4500, c. 5000, d. 8000, e. 9000
Example Output: a

Example Input: Problem: the wages earned by robin is 38 % more than that earned by erica. the wages earned by charles is 60 % more than that earned by erica. how much % is the wages earned by charles more than that earned by robin ?
Options: a. 23 %, b. 27.53 %, c. 30 %, d. 50 %, e. 100 %
Example Output:
b