You are given a math word problem and you are supposed to make use of mathematical concepts like probability, combinatorics, linear equations, sequences/series, or simple operators like addition, subtraction, division, or multiplication to answer the given question. Choose the best option from the 5 given options and report that option.

[Q]: Question: A reduction of 20% in the price of salt enables a lady to obtain 10kgs more for Rs.100, find the original price per kg?

Option A: Rs.2.9

Option B: Rs.2.1

Option C: Rs.2.5

Option D: Rs.2.2

Option E: Rs.2.7
[A]: Option C

[Q]: Question: If f(y)=y^2 and y is a positive integer, which of the following CANNOT be the value of f(f(y))?

Option A: 1

Option B: 144

Option C: 81

Option D: 16

Option E: 256
[A]: Option B

[Q]: Question: A man's basic pay for a 40 hour week is Rs.20. Overtime is paid for at 25% above the basic rate. In a certain week he worked overtime and his total wage was Rs.25. He therefore worked for a total of :

Option A: 45 hours

Option B: 47 hours

Option C: 48 hours

Option D: 50 hours

Option E: None
[A]:
Option C