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: what will be the difference between simple and compound interest at 16 % per annum on a sum of rs . 1000 after 4 years ? 
Options: a ) 164.19 , b ) 164.12 , c ) 170.6 , d ) 167.1 , e ) 165.11
Example Output: c

Example Input: Problem: a retailer bought a machine at a wholesale price of $ 90 and later on sold it after a 10 % discount of the retail price . if the retailer made a profit equivalent to 20 % of the whole price , what is the retail price t of the machine ? 
Options: a ) 81 , b ) 100 , c ) 120 , d ) 135 , e ) 160
Example Output: c

Example Input: Problem: a fruit seller sells mangoes at the rate of rs . 9 per kg and thereby loses 20 % . at what price per kg , he should have sold them to make a profit of 5 % ? 
Options: a ) rs . 11.81 , b ) rs . 12 , c ) rs . 12.25 , d ) rs . 12.31 , e ) none
Example Output:
a