In this task, you need to answer the given multiple-choice question on the gain. Gain is the value by which to multiply the input. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

[EX Q]: Problem: solve the quickfire maths brain teaser â ˆ š 25 % = ? 
Options: a ) 30 % , b ) 40 % , c ) 50 % , d ) 19 % , e ) 29 %
[EX A]: c

[EX Q]: Problem: if 40 % of a certain number is 160 , then what is 30 % of that number ? 
Options: a ) 270 , b ) 380 , c ) 120 , d ) 360 , e ) 180
[EX A]: c

[EX Q]: Problem: the price of a book is increased from $ 300 to $ 390 . what is the % of increase in its price ? 
Options: a ) 10 % , b ) 20 % , c ) 30 % , d ) 35 % , e ) 45 %
[EX A]:
c