instruction:
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.
question:
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
answer:
a

question:
Problem: there is one 4 - digit whole number n, such that the last 4 digits of n 2 are in fact the original number n
Options: a. 8476, b. 7376, c. 9376, d. 7378, e. 9466
answer:
c

question:
Problem: a shopkeeper forced to sell at cost price, uses a 950 grams weight for a kilogram. what is his gain percent ?
Options: a. 10 %, b. 9 %, c. 11.11 %, d. 5.26 %, e. none of these
answer:
d