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: the average age of 17 persons in a office is 15 years. out of these, the average age of 5 of them is 14 years and that of the other 9 persons is 16 years. the age of the 15 th person is ?
Options: a. 39, b. 41, c. 45, d. 42, e. 50
b

Problem: a train 150 m long is running at a speed of 68 kmph. how long does it take to pass a man who is running at 8 kmph in the same direction as the train ?
Options: a. 2 sec, b. 6 sec, c. 8 sec, d. 9 sec, e. 5 sec
d

Problem: 12.5 * 3.2 * 7.8 = ?
Options: a. 312, b. 435, c. 224, d. 646, e. 742

a