Definition: 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: a man is 24 years older than his son. in six years, his age will be twice the age of his son. the present age of the son is
Options: a. 14 years, b. 28 years, c. 20 years, d. 22 years, e. none
Output:
e