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 rs . 420 amount to rs . 540 in 4 years , what will it amount to in 6 years at the same rate % per annum ? 
Options: a ) s . 575 , b ) s . 595 , c ) s . 590 , d ) s . 600 , e ) s . 585
[EX A]: d

[EX Q]: Problem: the difference between the compound interest compounded annually and simple interest for 2 years at 20 % per annum is rs . 72 . find the principal ? 
Options: a ) 2277 , b ) 2667 , c ) 3600 , d ) 2766 , e ) 1800
[EX A]: e

[EX Q]: Problem: one night a certain hotel rented 4 / 5 of its rooms , including 2 / 3 of their air conditioned rooms . if 3 / 5 of its rooms were air conditioned , what percent of the rooms that were not rented were air conditioned ? 
Options: a ) 60 % , b ) 70 % , c ) 80 % , d ) 90 % , e ) 100 %
[EX A]:
e