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 profit percent is made by selling an article at a certain price , if by selling at 4 / 5 rd of that price , there would be a loss of 20 % ? 
Options: a ) 0 % , b ) 29 % , c ) 70 % , d ) 27 % , e ) 28 %
Example Output: a

Example Input: Problem: find the annual income derived by investing $ 6800 in 30 % stock at 136 . 
Options: a ) 550 , b ) 1500 , c ) 250 , d ) 1300 , e ) 400
Example Output: b

Example Input: Problem: an empty fuel tank with a capacity of 212 gallons was filled partially with fuel a and then to capacity with fuel b . fuel a contains 12 % ethanol by volume and fuel b contains 16 % ethanol by volume . if the full fuel tank contains 30 gallons of ethanol , how many gallons of fuel a were added ? 
Options: a ) 160 , b ) 98 , c ) 100 , d ) 80 , e ) 50
Example Output:
b