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: a bowl was filled with 10 ounces of water , and 0.00008 ounce of the water evaporated each day during a 50 - day period . what percent of the original amount of water evaporated during this period ? 
Options: a ) 0.004 % , b ) 0.04 % , c ) 0.40 % , d ) 4 % , e ) 40 %
Example Output: b

Example Input: Problem: a car dealership has 40 cars on the lot , 15 % of which are silver . if the dealership receives a new shipment of 80 cars , 30 % of which are not silver , what percentage of total number of cars are silver ? 
Options: a ) 20 % , b ) 25 % , c ) 30 % , d ) 35 % , e ) 40 %
Example Output: b

Example Input: Problem: a man can row downstream at the rate of 45 kmph and upstream at 23 kmph . find the man ’ s rate in still water and rate of current ? 
Options: a ) 8.5 , b ) 10.0 , c ) 12.5 , d ) 11.0 , e ) 8.25
Example Output:
d