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'.

[Q]: Problem: if each year the population of the country grows by 40 % , how many years will elapse before the population of the country doubles ? 
Options: a ) 3 , b ) 4 , c ) 5 , d ) 6 , e ) 7
[A]: a


[Q]: Problem: find the compound interest on $ 50000 in 2 years at 4 % per annum , the interest being compounded half - yearly ? 
Options: a ) $ 645.56 , b ) $ 4121.60 , c ) $ 954.26 , d ) $ 745.69 , e ) $ 1020.45
[A]: b


[Q]: Problem: the profit obtained by selling an article for rs . 86 is the same as the loss obtained by selling it for rs . 42 . what is the cost price of the article ? 
Options: a ) rs . 40 , b ) rs . 50 , c ) rs . 49 , d ) rs . 59 , e ) rs . 64
[A]:
e