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: the purchase price of an article is $ 48. in order to include 5 % of cost for overhead and to provide $ 12 of net profit, the markup should be
Options: a. 15 %, b. 25 %, c. 30 %, d. 40 %, e. 45 %
[A]: c


[Q]: Problem: a can contains a mixture of liquids a and b is the ratio 7: 5. when 18 litres of mixture are drawn off and the can is filled with b, the ratio of a and b becomes 7: 9. how many liter of liquid a was contained by the can initially ?
Options: a. 32, b. 52, c. 62, d. 42, e. 48
[A]:
d