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: the length of the bridge , which a train 140 metres long and travelling at 45 km / hr can cross in 30 seconds , is :
Options: a ) 200 m , b ) 235 m , c ) 245 m , d ) 250 m , e ) 270 m
[A]: b

[Q]: Problem: a train 120 m long running at 60 kmph crosses a platform in 20 sec . what is the length of the platform ?
Options: a ) 213 , b ) 298 , c ) 350 , d ) 726 , e ) 267
[A]: a

[Q]: Problem: ajay and balu together can do a piece of work in 12 days . balu and charan together can do the same work in 16 days . after ajay has been working at it for 5 days and balu for 7 days , charan finishes it in 13 days . in how many days will charan alone be able to do the work ?
Options: a ) 16 days , b ) 24 days , c ) 36 days , d ) 48 days , e ) 58 days
[A]:
b