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: a courtyard is 25 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 ) 16000 , b ) 18000 , c ) 20000 , d ) 22000 , e ) none of these

Ex Output:

c