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.

[Q]: Question: man buys an article for 10% less than its value and sells it for 10% more than its value. His gain or loss percent is?

 Option A: 12

 Option B: 76

 Option C: 26

 Option D: 20

 Option E: 12
[A]: Option D


[Q]: Question: On his first 3 tests, Rajeev received an average score of X points. If on his fourth test, he exceeds his previous average score by 24 points, what is his average score for his first 4 tests?

 Option A: X

 Option B: X+6

 Option C: X+4

 Option D: X+3

 Option E: X+2
[A]: Option B


[Q]: Question: For every even positive integer m, f(m) represents the product of all even integers from 2 to m, inclusive. For example, f(12)=2x4x6x8x10x12. What is the greatest prime factor of f(30)?

 Option A: 2

 Option B: 5

 Option C: 11

 Option D: 13

 Option E: 19
[A]:
Option D