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: two pipes a and b can separately fill a cistern in 24 minutes and 48 minutes respectively . there is a third pipe in the bottom of the cistern to empty it . if all the three pipes are simultaneously opened , then the cistern is full in 12 minutes . in how much time , the third pipe alone can empty the cistern ? 
Options: a ) 90 min , b ) 48 min , c ) 54 min , d ) 120 min , e ) 130 min

A: b
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Q: Problem: a and b finish the job in 15 days . while a , b and c can finish it in 11 days . c alone will finish the job in 
Options: a ) 41.25 days , b ) 30.25 days , c ) 60.25 days , d ) 71.25 days , e ) 51.25 days

A: a
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Q: Problem: what is the speed of the stream if a canoe rows upstream at 4 km / hr and downstream at 12 km / hr 
Options: a ) 1 kmph , b ) 4 kmph , c ) 3 kmph , d ) 2 kmph , e ) 1.9 kmph

A:
b
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