Instructions: 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.
Input: Problem: the price of lunch for 13 people was $ 207 including a 15 % gratuity for service. what was the average price per person, excluding the gratuity ?
Options: a. 11.73, b. 12, c. 13.85, d. 14, e. 15.87
Output:
c