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: walking with 4 / 5 of my usual speed , i arrive at the bus stop 7 minutes later than normal . how many minutes does it take to walk to the bus stop at my usual speed ? 
Options: a ) 12 , b ) 16 , c ) 20 , d ) 24 , e ) 28

A: e
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Q: Problem: a and b can do a piece of work in 8 days . with the help of c they finish the work in 4 days . c alone can do that piece of work in ? 
Options: a ) 40 days , b ) 20 days , c ) 8 days , d ) 60 days , e ) 40 days

A: c
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Q: Problem: one pipe can fill a tank three times as fast as another pipe . if together the two pipes can fill the tank in 36 minutes , then the slower pipe alone will be able to fill the tank in : 
Options: a ) 144 min , b ) 145 min , c ) 150 min , d ) 200 min , e ) 250 min

A:
a
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