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 trains a and b are 125 m and 150 m long and are moving at one another at 54 km / hr and 36 km / hr respectively . arun is sitting on coach b 1 of train a . calculate the time taken by arun to completely cross train b . 
Options: a ) 10 s , b ) 11 s , c ) 4 s , d ) 8 s , e ) 12 s
[A]: b


[Q]: Problem: x can finish a work in 20 days . y can finish the same work in 15 days . yworked for 9 days and left the job . how many days does x alone need to finish the remaining work ? 
Options: a ) 3 , b ) 5 , c ) 6 , d ) 8 , e ) 9
[A]: d


[Q]: Problem: one copy machine can make 30 copies a minute , and a second copy machine makes 20 copies a minute . if the two copiers work together , how long would it take them to make 2,000 copies ? 
Options: a ) 20 minutes , b ) 40 minutes , c ) 45 minutes , d ) 50 minutes , e ) 55 minutes
[A]:
b