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: 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: find the smallest number that should be multiplied with 54000 to make it a perfect cube.
Options: ['a. 4', 'b. 5', 'c. 6', 'd. 3', 'e. 7']
[EX A]: a

[EX Q]: Problem: the average weight of 8 person ' s increases by 2.5 kg when a new person comes in place of one of them weighing 66 kg. what might be the weight of the new person ?
Options: a. 56 kg, b. 90 kg, c. 86 kg, d. data inadequate, e. none of these
[EX A]:
c