You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
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.

From a pack of 52 cards, two cards are drawn together at random. What is the probability of both the cards being kings?

Option A:2/1223

Option B: 1/122

Option C: 1/221

Option D: 3/1253

Option E: 2/153

Solution: Option C
Why? Let s be the sample space.
Then n(s) = 52C2 = 1326
E = event of getting 2 kings out of 4
n(E) = 4C2 = 6
P(E) = 6/1326 = 1/221

New input: Question: There are two inlets and one outlet to a cistern. One of the inlets takes 4 hours to fill up the cistern and the other inlet takes twice as much time to fill up the same cistern. Both of the inlets are turned on at 8:30 AM with the cistern completely empty, and at 10:30AM, the outlet is turned on and it takes 1 more hour to fill the cistern completely. How much time does the outlet working alone takes to empty the cistern when the cistern is full?

Option A: 2 hours

Option B: 2.5 hours

Option C: 3 hours

Option D: 3.5 hours

Option E: 8 hours
Solution:
Option E