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: two passenger trains start at the same hour in the day from two different stations and move towards each other at the rate of 16 kmph and 21 kmph respectively . when they meet , it is found that one train has traveled 60 km more than the other one . the distance between the two stations is ? 
Options: a ) 2887 , b ) 444 , c ) 877 , d ) 278 , e ) 178
b

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
a

Problem: a is twice as fast as b . if b alone can do a piece of work in 10 days , in what time can a and b together complete the work ? 
Options: a ) 10 / 3 , b ) 8 , c ) 9 , d ) 7 / 3 , e ) 12

a