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: 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: an error 1 % in excess is made while measuring the side of a square. the percentage of error in the calculated area of the square is :
Options: a. 2.01, b. 30.1, c. 3.01, d. 25.01, e. 4.05
[EX A]: a

[EX Q]: Problem: in what time will a railway train 52 m long moving at the rate of 24 kmph pass a telegraph post on its way ?
Options: a. 3 sec, b. 4 sec, c. 8 sec, d. 6 sec, e. 7 sec
[EX A]:
c