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: 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
[EX A]: Option C

[EX Q]: Question: When positive integer k is divided by 5, the remainder is 2. When k is divided by 6, the remainder is 5. If k is less than 24, what is the remainder when k is divided by 7?

Option A: 2

Option B: 5

Option C: 6

Option D: 3

Option E: 8
[EX A]: Option D

[EX Q]: Question: How many integers from 0 to 53, inclusive, have a remainder of 1 when divided by 3 ?

Option A: 15

Option B: 16

Option C: 17

Option D: 18

Option E: 19
[EX A]:
Option D