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 fill a cistern in 20 and 30 minutes respectively, and a third pipe C can empty it in 40 minutes. How long will it take to fill the cistern if all the three are opened at the same time?

 Option A: 17 1/5

 Option B: 17 1/8

 Option C: 17 1/7

 Option D: 17 1/1

 Option E: 17 1/2
Option C

Question: In a certain Gun shooting competition prizes were awarded as follows: the first place winner receives 11 points, the second place winner receives 7 points, the third place winner receives 5 points and the fourth place winner receives 2 points . No other points were awarded. John participated several times in the competition. The product of all the points he received was 84700. How many times did he participate in the competition.

 Option A: 7

 Option B: 5

 Option C: 3

 Option D: 2

 Option E: cannot be determined
Option E

Question: Jerry went to a shop and bought things worth Rs. 30, out of which 30 % went on sales tax on taxable purchases. If the tax rate was 6%, then what was the cost of the tax free items?

 Option A: 19

 Option B: 19.7

 Option C: 21.3

 Option D: 21.5

 Option E: 24.7

Option E