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: calculate how many seconds it will take for 4 bells to toll together again , given that they begin to toll together respectively at the intervals of 9 , 10 , 14 and 18 seconds . ? 
Options: a ) 636 , b ) 631 , c ) 633 , d ) 610 , e ) 630
[EX A]: e

[EX Q]: Problem: from the beginning to the end of 2007 , the price of a stock rose 20 percent . in 2008 , it dropped 25 percent . in 2009 , it rose 25 percent . what percent of the stock â € ™ s 2007 starting price was the price of the stock at the end of 2009 ? 
Options: a ) 80 , b ) 90 , c ) 95 , d ) 100 , e ) 112.5
[EX A]: e

[EX Q]: Problem: after 10 % of the inhabitants of a village disappeared , a panic set in during which 25 % of the remaining inhabitants left the village . at that time , the population was reduced to 4860 . what was the number of original inhabitants ? 
Options: a ) 7000 , b ) 7200 , c ) 7400 , d ) 7600 , e ) 7800
[EX A]:
b