You are given a math word problem and you are supposed to make use of mathematical concepts like probability, combinatorics, linear equations, sequences/series, or simple operators like addition, subtraction, division, or multiplication to answer the given question. Choose the best option from the 5 given options and report that option.

Input: Consider Input: Question: By selling 12 toffees for a rupee, a man loses 20%. How many for a rupee should be sell to get a gain of 20%?

Option A: 5

Option B: 8

Option C: 10

Option D: 15

Option E: 20

Output: Option B

Input: Consider Input: Question: The time taken by a man to row his boat upstream is twice the time taken by him to row the same distance downstream. If the speed of the boat in still water is 42 kmph, find the speed of the stream?

Option A: 12

Option B: 15

Option C: 14

Option D: 18

Option E: 19

Output: Option C

Input: Consider Input: Question: A rectangular field is to be fenced on three sides leaving a side of 20 feet uncovered. If the area of the field is 680 sq. feet, how many feet of fencing will be required?

Option A: 34

Option B: 40

Option C: 68

Option D: 88

Option E: 78
Output: Option D