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: ram , who is half as efficient as krish , will take 27 days to complete a task if he worked alone . if ram and krish worked together , how long will they take to complete the task ? 
Options: a ) 16 days , b ) 12 days , c ) 9 days , d ) 6 days , e ) 18 days
c

Problem: jack and jill are marathon runners . jack can finish a marathon ( 42 km ) in 3.5 hours and jill can run a marathon in 4.2 hours . what is the ratio of their average running speed ? ( jack : jill ) 
Options: a ) 14 / 15 , b ) 15 / 14 , c ) 4 / 5 , d ) 6 / 5 , e ) can not be determined
d

Problem: a man can row upstream at 25 kmph and downstream at 41 kmph , and then find the speed of the man in still water ? 
Options: a ) 33 , b ) 67 , c ) 30 , d ) 15 , e ) 17

a