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: tickets to a certain concert sell for $ 20 each . the first 10 people to show up at the ticket booth received a 40 % discount , and the next 20 received a 15 % discount . if 50 people bought tickets to the concert , what was the total revenue from ticket sales ? 
Options: a ) $ 600 , b ) $ 740 , c ) $ 860 , d ) $ 980 , e ) $ 1,140
[EX A]: c

[EX Q]: Problem: if difference between compound interest and simple interest on a sum at 10 % p . a . for 2 years is rs . 150 then sum is 
Options: a ) s . 15000 , b ) s . 15100 , c ) s . 15800 , d ) s . 16000 , e ) s . 16200
[EX A]: a

[EX Q]: Problem: a sum of money at simple interest amounts to rs . 815 in 3 years and to rs . 844 in 4 years . the sum is : 
Options: a ) s . 650 , b ) s . 690 , c ) s . 698 , d ) s . 728 , e ) s . 760
[EX A]:
d