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: 8 persons can build a wall 140 m long in 42 days . in how many days can 30 persons complete a similar wall 100 m long ? 
Options: a ) 12 , b ) 10 , c ) 8 , d ) 6 , e ) 5

A: c
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Q: Problem: in what time will a railway train 60 m long moving at the rate of 36 kmph pass a telegraph post on its way ? 
Options: a ) 2 , b ) 7 , c ) 8 , d ) 6 , e ) 9

A: d
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Q: Problem: a , b , k start from the same place and travel in the same direction at speeds of 30 km / hr , 40 km / hr , 60 km / hr respectively . b starts four hours after a . if b and k overtake a at the same instant , how many hours after a did k start ? 
Options: a ) 3 , b ) 4.5 , c ) 8 , d ) d ) 5.5 , e ) e ) 5

A:
c
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