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.

[Q]: Problem: each of the three people individually can complete a certain job in 3, 4, and 6 hours, respectively. what is the lowest fraction of the job that can be done in 1 hour by 2 of the people working together at their respective rates ?
Options: a. 1 / 3, b. 9 / 20, c. 8 / 15, d. 5 / 12, e. 2 / 3
[A]: d


[Q]: Problem: a man swims downstream 36 km and upstream 18 km taking 3 hours each time, what is the speed of the man in still water ?
Options: a. 7, b. 8, c. 9, d. 2, e. 4
[A]: c


[Q]: Problem: 40 persons like apple. 7 like orange and mango dislike apple. 10 like mango and apple and dislike orange. 3 like all. how many people like apple ?
Options: a. 47, b. 46, c. 54, d. 58, e. 62
[A]:
b