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'.

Q: Problem: at what rate percent per annum will the simple interest on a sum of money be 1 / 5 of the amount in 10 years ? 
Options: a ) 2 % , b ) 7 % , c ) 9 % , d ) 3 % , e ) 1 %

A: a
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Q: Problem: a sum was put a simple interest at a certain rate for 2 years . had it been put at 4 % higher rate , it would have fetched rs . 60 more . the sum is : 
Options: a ) rs . 750 , b ) rs . 700 , c ) rs . 820 , d ) rs . 940 , e ) rs . 900

A: a
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Q: Problem: chlorination is used in industry for the purification of water ; 1 gm solution of chlorine will remove half of the germs in 1 liter of water . if water containing less than 0.09 % of germs is considered clean , what is the minimum amount of chlorine required to purify 150 liter of water containing 0.3 liter of harmful substances ? 
Options: a ) 1 , b ) 2 , c ) 3 , d ) 4 , e ) 5

A:
b
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