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: jake can dig a well in 16 days . paul can dig the same well in 24 days . jake , paul and hari together dig the well in 8 days . hari alone can dig the well in 
Options: a ) 96 days , b ) 48 days , c ) 32 days , d ) 24 days , e ) 28 days
[A]: b


[Q]: 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
[A]: d


[Q]: Problem: a tank is filled by 3 pipes a , b , c in 3 hours . pipe c is twice as fast as b and b is twice as fast as a . how much will pipe a alone take to fill the tank ? 
Options: a ) 25 hr , b ) 35 hr , c ) 40 hr , d ) 20 hr , e ) 21 hr
[A]:
e