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'.

Problem: calculate how long it will take a swimmer to swim a distance of 3 km against the current of a river which flows at 1.7 km / hr , given that he can swim in still water at 3 km / h 
Options: a ) 2.31 , b ) 9.31 , c ) 1.31 , d ) 4.31 , e ) 3.31
a