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.

Example Input: Question: Two pipes A and B can separately fill a cistern in 10 and 15 minutes respectively. A person opens both the pipes together when the cistern should have been was full he finds the waste pipe open. He then closes the waste pipe and in another 4 minutes the cistern was full. In what time can the waste pipe empty the cistern when fill?

 Option A: 7

 Option B: 9

 Option C: 5

 Option D: 4

 Option E: 8
Example Output: Option E

Example Input: Question: The number which exceeds 16% of it by 42 is?

 Option A: 50

 Option B: 25

 Option C: 52

 Option D: 58

 Option E: 60
Example Output: Option A

Example Input: Question: Alka bought 15 books for Rs.2580 from one shop and 20 books for Rs.920 from another. What is the average price he paid per book ?

 Option A: 104

 Option B: 181

 Option C: 100

 Option D: 35

 Option E: 20
Example Output:
Option C