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: a crow leaves its nest , and flies back and forth from its nest to a nearby ditch to gather worms . the distance between the nest and the ditch is 100 meters . in one and a half hours , the crow manages to bring worms to its nest 15 times . what is the speed of the crow in kilometers per hour ? 
Options: a ) 1 , b ) 2 , c ) 3 , d ) 5 , e ) 7

A: d
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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
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Q: Problem: a metal company ' s old machine makes bolts at a constant rate of 100 bolts per hour . the company ' s new machine makes bolts at a constant rate of 150 bolts per hour . if both machines start at the same time and continue making bolts simultaneously , how many minutes will it take the two machines to make a total of 500 bolts ? 
Options: a ) 36 , b ) 72 , c ) 120 , d ) 144 , e ) 180

A:
c
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