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: ages of two persons differ by 20 years. if 6 year ago, the elder one be 3 times as old the younger one, find their present age
Options: a. 12,28, b. 14,30, c. 16,36, d. 18,34, e. 19,34
[A]: c


[Q]: Problem: how many prime numbers are between 76 / 8 and 124 / 5 ?
Options: a. 1, b. 2, c. 3, d. 4, e. 5
[A]: e


[Q]: Problem: a certain number when divided by 39 leaves a remainder 20, what is the remainder when the same number is divided by 13 ?
Options: a. 7, b. 8, c. 9, d. 0, e. 1
[A]:
a