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'.

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
c

Problem: in what time will a train 20 m long cross an electric pole , it its speed be 144 km / hr ? 
Options: a ) 2.5 sec , b ) 2.8 sec , c ) 0.5 sec , d ) 2.3 sec , e ) 1.5 sec
c

Problem: a train 700 m long can cross an electric pole in 40 sec and then find the speed of the train ? 
Options: a ) 987 , b ) 271 , c ) 72 , d ) 27 , e ) 63

e