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: In a class of 40 students, 10 did not opt for math. 15 did not opt for science and 2 did not opt for either. How many students of the class opted for both math and science?

 Option A: 13

 Option B: 15

 Option C: 7

 Option D: 17

 Option E: 18
[EX A]: Option C

[EX Q]: Question: Patrick purchased 80 pencils and sold them at a loss equal to the selling price of 16 pencils. The cost of 80 pencils is how many times the selling price of 80 pencils?

 Option A:  0.75

 Option B:  1.2

 Option C:  1.8

 Option D:  2.4

 Option E:  4.25
[EX A]: Option B

[EX Q]: Question: A metal company's old machine makes bolts at a constant rate of 100 bolts per hour. The company's new machine makes bolts at a constant rate of 150 bolts per hour. If both machines start at the same time and continue making bolts simultaneously, how many minutes will it take the two machines to make a total of 400 bolts?

 Option A:  36

 Option B:  72

 Option C:  96

 Option D:  144

 Option E:  180
[EX A]:
Option C