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: a man has $ 10,000 to invest . he invests $ 4000 at 5 % and $ 3500 at 4 % . in order to have a yearly income of $ 500 , he must invest the remainder at : 
Options: a ) 4.6 % , b ) 3.6 % , c ) 6.4 % , d ) 7.8 % , e ) 8.9 %
c

Problem: what annual installment will discharge a debt of rs . 1092 due in 3 years at 12 % simple interest ? 
Options: a ) 442 , b ) 441 , c ) 440 , d ) 320 , e ) 532
a

Problem: a trader cheats both his supplier and customer by using faulty weights . when he buys from the supplier , he takes 10 % more than the indicated weight . when he sells to his customer , he gives the customer a weight such that 10 % of that is added to the weight , the weight claimed by the trader is obtained . if he charges the cost price of the weight that he claims , find his profit percentage . 
Options: a ) 20 % , b ) 21 % , c ) 21.33 % , d ) 22.109 % , e ) 23 %

b