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: in a certain pond , 40 fish were caught , tagged , and returned to the pond . a few days later , 40 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 is the approximate number of fish in the pond ?
Options: a ) 1000 , b ) 625 , c ) 1,250 , d ) 2,500 , e ) 10,000
[EX A]: a

[EX Q]: Problem: a man can row his boat with the stream at 16 km / h and against the stream in 12 km / h . the man ' s rate is ?
Options: a ) 8 kmph , b ) 9 kmph , c ) 2 kmph , d ) 4 kmph , e ) 1 kmph
[EX A]: c

[EX Q]: Problem: what annual payment will discharge a debt of rs . 1030 due in 2 years at the rate of 5 % compound interest ?
Options: a ) 553.94 , b ) 551.25 , c ) 534.33 , d ) 543.33 , e ) 646.33
[EX A]:
a