Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

[EX Q]: Problem: the size of a television screen is given as the length of the screen ' s diagonal. if the screens were flat, then the area of a square 19 - inch screen would be how many square inches greater than the area of a square 17 - inch screen ?
Options: a. 36, b. 4, c. 16, d. 38, e. 40
[EX A]: a

[EX Q]: Problem: what is the rate percent when the simple interest on rs. 720 amount to rs. 180 in 4 years ?
Options: a. 6.25, b. 7.25, c. 8.25, d. 9.25, e. 10.25
[EX A]: a

[EX Q]: Problem: a man is 12 years older than his brother. in two years, his age will be twice the age of his brother. the present age of his brother is :
Options: a. 10, b. 21, c. 22, d. 23, e. 24
[EX A]:
a