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: jack has two dice, one has 6 equally probable sides, labeled 1, 2, 3, 4, 5, 6, and the other has 7 equally probable sides, labeled 1, 2, 3, 4, 5, 6, 7. if jack rolls both dice what is the probability that both of the number ' s sum will be 13 ?
Options: a. 3 / 14, b. 2 / 7, c. 1 / 3, d. 1 / 42, e. 12 / 21
d

Problem: a sells a bicycle to b and makes a profit of 50 %. b sells the same bicycle to c at a profit of 25 %. if the final s. p. of the bicycle was rs. 225, find out the cost price of the bicycle for a.
Options: a. 237, b. 126, c. 971, d. 611, e. 120
e

Problem: the average age of father and his two sons is 24 years. 5 years ago, the average age of the two sons was 15 years. if the difference between the ages of the two sons is 4 years, what is the present age of the father ?
Options: a. 45, b. 32, c. 47, d. 48, e. 49

b