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: in one hour, a boat goes 19 km / hr along the stream and 9 km / hr against the stream. the speed of the boat in still water ( in km / hr ) is :
Options: a. 12 kmph, b. 13 kmph, c. 14 kmph, d. 15 kmph, e. 16 kmph

Output: c


Input: Consider Input: Problem: subtracting 3 % of a from a is equivalent to multiplying a by how much ?
Options: a. 0.97, b. 9.4, c. 0.094, d. 94, e. none

Output: a


Input: Consider Input: Problem: two - third of a positive number and 144 / 216 of its reciprocal are equal. the number is :
Options: a. 5 / 12, b. 12 / 5, c. 25 / 144, d. 144 / 25, e. 1


Output: e