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 train , 800 meter long is running with a speed of 78 km / hr . it crosses a tunnel in 1 minute . what is the length of the tunnel ? 
Options: a ) 650 meter , b ) 555 meter , c ) 500 meter , d ) 458 meter , e ) none of these

A: c
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Q: Problem: a tank can be filled by two pipes a and b in 60 minutes and 40 minutes respectively . how many minutes will it take to fill the tank from empty state if b is used for the first half time and then a and b fill it together for the other half . 
Options: a ) 15 mins , b ) 20 mins , c ) 25 mins , d ) 30 mins , e ) 35 mins

A: d
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Q: Problem: a plane flies 420 miles with the wind and 350 miles against the wind in the same length of time . if the speed of the wind is 23 mph , what is the speed of the plain in still air ? 
Options: a ) 253 mph . , b ) 275 mph . , c ) 296 mph . , d ) 278 mph . , e ) 235 mph .

A:
a
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