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: A and B complete a work in 6 days. A can alone can do it in 10 days. If both can together can do the work in how many days?

 Option A: 7

 Option B: 3.75

 Option C: 2

 Option D: 1

 Option E: 8
[EX A]: Option B

[EX Q]: Question: Two pipes A and B can fill a tank in 15 min and 20 min respectively. Both the pipes are opened together but after 4 min, pipe A is turned off. What is the total time required to fill the tank?

 Option A: 14 min 19 sec

 Option B: 14 min 42 sec

 Option C: 14 min 20 sec

 Option D: 14 min 40 sec

 Option E: 14 min 10 sec
[EX A]: Option D

[EX Q]: Question: A certain barrel, which is a right circular cylinder, is filled to capacity with 60 gallons of oil. The first barrel is poured into a second barrel, also a right circular cylinder, which is empty. The second barrel is twice as tall as the first barrel and has twice the diameter of the first barrel. If all of the oil in the first barrel is poured into the second barrel, how much empty capacity, in gallons, is left in the second barrel?

 Option A: There is no empty capacity

 Option B: 100 gallons

 Option C: 300 gallons

 Option D: 420 gallons

 Option E: 840 gallons
[EX A]:
Option D