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: a train of 25 carriages, each of 60 meters length, when an engine also of 60 meters length is running at a speed of 60 kmph. in what time will the train cross a bridge 1.0 km long ?
Options: a. 2.5, b. 3, c. 5, d. 7, e. 9
a

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: some of 45 % - intensity red paint is replaced with 25 % solution of red paint such that the new paint intensity is 40 %. what fraction of the original paint was replaced ?
Options: a. 2 / 5, b. 1 / 4, c. 1 / 5, d. 1 / 7, e. 2 / 3

b