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: Question: A cistern can be filled by a tap in 3 hours while it can be emptied by another tap in 9 hours. If both the taps are opened simultaneously, then after how much time will the cistern get filled?

Option A: 2.9 hrs

Option B: 4.5 hrs

Option C: 2.9 hrs

Option D: 7.2 hrs

Option E: 8.6 hrs

Answer: Option B

Question: Question: A certain car dealership offers its newest model in ten exterior and six interior colors. If the ten interior colors are identical to the ten exterior colors, and the dealership sells every pair of colors except those that would result in a car with an identically colored interior and exterior, how many different color combinations are possible?

Option A: 45

Option B: 81

Option C: 90

Option D: 10!/2!

Option E: 36

Answer: Option E

Question: Question: The area of the square formed on the diagonal of a rectangle as its side is 108 1/3 % more than the area of the rectangle. If the perimeter of the rectangle is 28 units, find the difference between the sides of the rectangle?

Option A: 7m

Option B: 6m

Option C: 5m

Option D: 2m

Option E: 4m

Answer:
Option D