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 5 / 4 of my usual speed , i miss the bus by 5 minutes . what is my usual time ? 
Options: a ) 18 , b ) 19 , c ) 20 , d ) 22 , e ) 24

A: c
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Q: Problem: a garrison of 2000 men has provisions for 54 days . at the end of 15 days , a reinforcement arrives , and it is now found that the provisions will last only for 30 days more . what is the reinforcement ? 
Options: a ) 1800 men , b ) 3900 men , c ) 600 men , d ) 3800 men , e ) 900 men

A: c
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Q: Problem: a train 400 m long is running at a speed of 78 km / hr . if it crosses a tunnel in 1 min , then the length of the tunnel is ? 
Options: a ) 277 m , b ) 700 m , c ) 900 m , d ) 187 m , e ) 1678 m

A:
c
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