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'.

[EX Q]: Problem: a man can do a piece of work in 4 days , but with the help of his son he can do it in 3 days . in what time can the son do it alone ? 
Options: a ) 12 days , b ) 6 days , c ) 5 days , d ) 4 days , e ) none of these
[EX A]: a

[EX Q]: Problem: a train overtakes two person who are walking in the same direction in which the train is going , at the rate of 2 kmph and 4 kmph and passes them completely in 9 and 10 seconds respectively . the length of the train is : 
Options: a ) 45 m , b ) 50 m , c ) 54 m , d ) 72 m , e ) none of these
[EX A]: b

[EX Q]: Problem: a participated in cycling contest and he drove the lap at the rate of 6 kmph , 12 kmph , 18 kmph , 24 kmph . . what is his average speed ? 
Options: a ) 15 kmph , b ) 18 kmph , c ) 14.25 kmph , d ) 11.52 kmph , e ) 16 kmph
[EX A]:
d