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.
Q: Problem: 1 / 2,16, 4,15, 3,56, _ ?
Options: a. 28 / 3, b. 27 / 3, c. 26 / 3, d. 25 / 3, e. 24 / 3
A: 
a