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'.

[EX Q]: Problem: if 40 % of a number is greater than 80 % of 5 by 2 , what is the number ? 
Options: a ) 3 , b ) 15 , c ) 20 , d ) 2 , e ) 5
[EX A]: b

[EX Q]: Problem: working alone , mary can pave a driveway in 4 hours and hillary can pave the same driveway in 3 hours . when they work together , mary thrives on teamwork so her rate increases by 33.33 % , but hillary becomes distracted and her rate decreases by 50 % . if they both work together , how many hours will it take to pave the driveway ? 
Options: a ) 2 hours , b ) 4 hours , c ) 5 hours , d ) 6 hours , e ) 7 hours
[EX A]: a

[EX Q]: Problem: in a certain pond , 55 fish were caught , tagged , and returned to the pond . a few days later , 55 fish were caught again , of which 2 were found to have been tagged . if the percent of tagged fish in the second catch approximates the percent of tagged fish in the pond , what ` s the approximate number of fish in the pond ? 
Options: a ) 400 , b ) 625 , c ) 1250 , d ) 1528 , e ) 10 000
[EX A]:
d