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: 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
Option C

Question: Ajay marked the price of his goods 30% more than his C.P. He then sells 1/4th of his stock at a discount of 15%, and half of the stock at the marked price, and the rest at a discount of 30%. Find his gain percentage.

 Option A: 16.5%

 Option B: 15.375%

 Option C: 14.20%

 Option D: 13.37%

 Option E: None of these
Option B

Question: Let A, B, and C be three points on circle O such that AC is a diameter of O. Extend line AC
to a point D such that DB is tangent to O at B, and suppose that \ADB = 20o. Compute
\ACB.

 Option A: 32o

 Option B: 47o

 Option C: 55o

 Option D: 68o

 Option E: 71o

Option C