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.

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
Option E

Question: Mr. Kramer, the losing candidate in a two-candidate election, received 942,568 votes, which was exactly 35 percent of all votes cast. Approximately what percent of the remaining votes would he need to have received in order to have won at least 50 percent of all the votes cast?

 Option A: 10%

 Option B: 12%

 Option C: 15%

 Option D: 17%

 Option E: 23%
Option E

Question: In a college, 70 percent of students study math, 75 percent of students study English, 85 percent study French and 80 percent study German.
Can you find out the percentage of students who study all 4 subjects ?

 Option A: 12%

 Option B: 10%

 Option C: 16%

 Option D: 18%

 Option E: 19%

Option B