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 Input:
Problem: 28 machines can do a work in 10 days . how many machines are needed to complete the work in 40 days ? 
Options: a ) 10 , b ) 6 , c ) 4 , d ) 7 , e ) 5

Ex Output:
d


Ex Input:
Problem: a man can row upstream at 5 kmph and downstream at 25 kmph , and then find the speed of the man in still water ? 
Options: a ) 15 , b ) 77 , c ) 30 , d ) 88 , e ) 34

Ex Output:
a


Ex Input:
Problem: an engineer undertakes a project to build a road 10 km long in 150 days and employs 30 men for the purpose . after 50 days , he finds only 2 km of the road has been completed . find the ( approximate ) number of extra men he must employ to finish the work in time . 
Options: a ) 22 , b ) 30 , c ) 15 , d ) 18 , e ) 20

Ex Output:

b