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'.

[Q]: 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
[A]: c


[Q]: Problem: you hold some gold in a vault as an investment . over the past year the price of gold increases by 40 % . in order to keep your gold in the vault , you must pay 5 % of the total value of the gold per year . what percentage has the value of your holdings changed by over the past year . 
Options: a ) 35 % , b ) 33 % , c ) 36 % , d ) 38 % , e ) 40 %
[A]: b


[Q]: Problem: alex and brian start a business with rs . 7000 each , and after 8 months , brian withdraws half of his capital . how should they share the profits at the end of the 18 months ? 
Options: a ) 5 : 4 , b ) 4 : 3 , c ) 18 : 11 , d ) 3 : 2 , e ) 18 : 13
[A]:
e