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'.

Example Input: Problem: vijay sells a cupboard at 10 % below cost price . had he got rs . 1500 more , he would have made a profit of 10 % . what is the cost price of the cupboard ? 
Options: a ) 7450 , b ) 7500 , c ) 7400 , d ) 7500 , e ) none of these
Example Output: b

Example Input: Problem: at what rate percent per annum will the simple interest on a sum of money be 4 / 5 of the amount in 10 years ? 
Options: a ) 4 % , b ) 7 % , c ) 8 % , d ) 3 % , e ) 1 %
Example Output: c

Example Input: Problem: a 6 litre sol is 20 % alcohol . how many litres of pure alcohol must be added to produce a sol that is 50 % alcohol ? 
Options: a ) a . 0.6 , b ) b . 1 , c ) c . 2.1 , d ) d . 3.6 , e ) e . 5.4
Example Output:
d