instruction:
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'.
question:
Problem: the speed at which a man can row a boat in still water is 15 km / hr . if he rows downstream , where the speed of current is 3 km / hr , how many seconds will he take to cover 90 meters ? 
Options: a ) 12 , b ) 16 , c ) 17 , d ) 18 , e ) 20
answer:
d


question:
Problem: if 42 men do a work in 25 days , in how many days will 50 men do it ? 
Options: a ) 23 , b ) 22 , c ) 19 , d ) 20 , e ) 21
answer:
e


question:
Problem: a work which could be finished in 8 days was finished 3 days earlier after 10 more men joined . the number of men employed was ? 
Options: a ) 22 , b ) 30 , c ) 88 , d ) 71 , e ) 11
answer:

b