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: 45 men working 8 hours per day dig 40 m deep . how many extra men should be put to dig to a depth of 50 m working 6 hours per day ?
Options: a ) 10 , b ) 20 , c ) 30 , d ) 40 , e ) 50
[A]: c

[Q]: Problem: a can finish a work in 20 days , b in 15 days and c in 12 days . b and c start the work but are forced to leave after 2 days . the remaining work was done by a in :
Options: a ) 10 , b ) 11 , c ) 12 , d ) 13 , e ) 14
[A]: e

[Q]: Problem: a train 300 meters long completely crosses a 300 meters long bridge in 45 seconds . what is the speed of the train is ?
Options: a ) 32 , b ) 48 , c ) 29 , d ) 27 , e ) 21
[A]:
b