In this task, you need to answer the given multiple-choice question on the general math. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

[EX Q]: Problem: a sum of money lent out at s . i . amounts to a total of $ 480 after 2 years and to $ 680 after a further period of 5 years . what was the initial sum of money that was invested ? 
Options: a ) $ 360 , b ) $ 380 , c ) $ 400 , d ) $ 420 , e ) $ 440
[EX A]: c

[EX Q]: Problem: mary ' s income is 60 % more than tim ' s income and tim ' s income is 10 % less than juan ' s income . what % of juan ' s income is mary ' s income . 
Options: a ) 144 % , b ) b . 120 % , c ) 96 % , d ) 80 % , e ) 64 %
[EX A]: a

[EX Q]: Problem: ages of two sisters differ by 9 years . if 5 years ago , the elder one was twice as old the younger one , find their present age 
Options: a ) 1228 , b ) 1423 , c ) 1632 , d ) 1834 , e ) 1932
[EX A]:
b