Instructions: 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.
Input: Problem: a man can row a distance of 5 km in 60 min with the help of the tide. the direction of the tide reverses with the same speed. now he travels a further 20 km in 10 hours. how much time he would have saved if the direction of tide has not changed ?
Options: a. 2, b. 8, c. 1, d. 6, e. 5
Output:
d