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 Input:
Problem: i sold a book at a profit of 10 % . had i sold it for $ 150 more , 15 % would have been gained . find the cost price ? 
Options: a ) $ 2000 , b ) $ 2500 , c ) $ 3000 , d ) $ 3120 , e ) $ 1540

Ex Output:
c


Ex Input:
Problem: if 15 % of 40 is greater than 25 % of a number by 2 , the number is 
Options: a ) 14 , b ) 16 , c ) 18 , d ) 20 , e ) 22

Ex Output:
b


Ex Input:
Problem: how long will a boy take to run round a square field of side 50 meters , if he runs at the rate of 10 km / hr ? 
Options: a ) 52 sec , b ) 45 sec , c ) 72 sec , d ) 25 sec , e ) 39 sec

Ex Output:

c