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.

[EX Q]: Question: Find the average of all the numbers between 11 and 36 which are divisible by 5

 Option A: 15

 Option B: 20

 Option C: 25

 Option D: 30

 Option E: 35
[EX A]: Option C

[EX Q]: Question: When n is divided by 19, the remainder is 7. When n is divided by 11, the quotient is equal to Z, and the remainder is equal to 7. Z must be divisible by which of the following numbers?

 Option A: 16

 Option B: 18

 Option C: 20

 Option D: 19

 Option E: 22
[EX A]: Option D

[EX Q]: Question: Pipe A can fill a tank in 6 hours. Due to a leak at the bottom, it takes 9 hours for the pipe A to fill the tank. In what time can the leak alone empty the full tank?

 Option A: 33

 Option B: 77

 Option C: 18

 Option D: 99

 Option E: 66
[EX A]:
Option C