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'.

Problem: if 20 typists can type 48 letters in 20 minutes , then how many letters will 30 typists working at the same rate complete in 1 hour ? 
Options: a ) 63 , b ) 72 , c ) 144 , d ) 216 , e ) 400
d

Problem: a 250 meter long train crosses a man standing on the platform in 12 sec . what is the speed of the train ? 
Options: a ) 228 , b ) 108 , c ) 1266 , d ) 75 , e ) 211
d

Problem: excluding stoppages , the speed of a bus is 60 kmph and including stoppages , it is 50 kmph . for how many minutes does the bus stop per hour ? 
Options: a ) 10 min , b ) 15 min , c ) 12 min , d ) 8 min , e ) 16 min

a