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: in what time will a train 50 m long cross an electric pole, it its speed be 360 km / hr ?
Options: a. 0.25, b. 0.5, c. 1.5, d. 2.5, e. 3.5
[EX A]: b

[EX Q]: Problem: a fort had provision of food for 150 men for 45 days. after 15 days, 10 men left the fort. the number of days for which the remaining food will last, is :
Options: a. 32, b. 37 1 / 4, c. 42, d. 54, e. 45
[EX A]: a

[EX Q]: Problem: a towel, when bleached, lost 30 % of its length and 25 % of its breadth. what is the percentage decrease in area ?
Options: a. 24 %, b. 30 %, c. 44 %, d. 54 %, e. 47.5 %
[EX A]:
e