You will be given a definition of a task first, then some input of the task.
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.

Problem: elvin ' s monthly telephone bill is the sum of the charge for the calls he made during the month and a fixed monthly charge for internet service. elvin ' s total telephone bill for january was $ 46 and elvin ' s total telephone bill for february was 76 $. if elvin ' s charge for the calls he made in february was twice the charge for the calls he made in january, what is elvin ' s fixed monthly charge for internet service ?
Options: a. $ 5, b. $ 10, c. $ 14, d. $ 16, e. $ 28
Output:
d