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 piece of work in 4 hours ; b and c together can do it in 3 hours , which a and c together can do it in 2 hours . how long will b alone take to do it ? 
Options: a ) 15 hours , b ) 14 hours , c ) 12 hours , d ) 74 hours , e ) 79 hours
[A]: c


[Q]: Problem: how many seconds will a train 250 meters long take to cross a platform 200 meters long if the speed of the train is 90 kmph ? 
Options: a ) 18 sec , b ) 15 sec , c ) 21 sec , d ) 16 sec , e ) 20 sec
[A]: a


[Q]: Problem: a can do a work in 15 days and b in 20 days . if they work on it together for 7 days , then the fraction of the work that is left is 
Options: a ) 8 / 17 , b ) 7 / 15 , c ) 3 / 15 , d ) 8 / 15 , e ) 11 / 60
[A]:
e