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: Consider Input: Problem: the speed of the boat in still water in 12 kmph. it can travel downstream through 48 kms in 3 hrs. in what time would it cover the same distance upstream ?
Options: a. 8 hours, b. 6 hours, c. 4 hours, d. 5 hours, e. 6 hours

Output: e


Input: Consider Input: Problem: in 10 years, a will be twice as old as b was 10 years ago. if a is now 5 years older than b the present age of b is
Options: a. 37, b. 38, c. 39, d. 35, e. 41

Output: d


Input: Consider Input: Problem: a can finish a piece of work in 4 days. b can do it in 10 days. they work together for two days and then a goes away. in how many days will b finish the work ?
Options: a. 3, b. 5, c. 6, d. 7, e. 8


Output: a