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'.

[EX Q]: Problem: if 20 typists can type 50 letters in 30 minutes , then how many letters will 40 typists working at the same rate complete in 1 hour ? 
Options: a ) 400 , b ) 500 , c ) 350 , d ) 250 , e ) 200
[EX A]: a

[EX Q]: Problem: a train 120 m long running at 60 kmph crosses a platform in 20 sec . what is the length of the platform ? 
Options: a ) 213 , b ) 298 , c ) 350 , d ) 726 , e ) 267
[EX A]: a

[EX Q]: Problem: a courtyard is 18 meter long and 16 meter board is to be paved with bricks of dimensions 20 cm by 10 cm . the total number of bricks required is ? 
Options: a ) 22877 , b ) 27778 , c ) 20000 , d ) 27999 , e ) 14400
[EX A]:
e