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

[Q]: Problem: a can do a work in 15 days and b in 20 days . if they work on it together for 5 days , then the fraction of the work that is left is : 
Options: a ) 1 / 3 , b ) 7 / 12 , c ) 5 / 12 , d ) 2 / 3 , e ) 1 / 2
[A]: c


[Q]: Problem: an seller earns an income of re 1 on the first day of his business . on every subsequent day , he earns an income which is just thrice of that made on the previous day . on the 20 th day of business , he earns an income of : 
Options: a ) 29 , b ) 57 , c ) 35 , d ) 20 , e ) 30
[A]: b


[Q]: Problem: two trains of equal length are running on parallel lines in the same direction at 46 km / hr and 36 km / hr . the faster train passes the slower train in 27 seconds . what is the length of each train ( in meters ) ? 
Options: a ) 50.5 , b ) 88.5 , c ) 37.5 , d ) 55.5 , e ) 23.5
[A]:
c