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.
--------
Question: Problem: a student travels from his house to school at 10 km / hr and reaches school 2 hours late. the next day he travels 18 km / hr and reaches school 1 hour early. what is the distance between his house and the school ?
Options: a. 65.0, b. 67.5, c. 70.0, d. 72.5, e. 75.0

Answer: b

Question: Problem: in a certain deck of cards, each card has a positive integer written on it, in a multiplication game a child draws a card and multiplies the integer on the card with the next large integer. if the each possible product is between 10 and 400, then the least and greatest integer on the card would be
Options: a. 3 and 15, b. 3 and 20, c. 4 and 13, d. 4 and 14, e. 5 and 14

Answer: b

Question: Problem: a boy swims downstream 56 km and upstream 42 km taking 7 hours each time; what is the speed of the current ?
Options: a. 5, b. 4, c. 3, d. 2, e. 1

Answer:
e