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: if the wheel is 14 cm then the number of revolutions to cover a distance of 968 cm is ? 
Options: a ) a ) 15 , b ) b ) 10 , c ) c ) 14 , d ) d ) 12 , e ) e ) 11

Ex Output:
e


Ex Input:
Problem: a man can row downstream at 25 kmph and upstream at 15 kmph . find the time to reach a destination point at a distance of 50 km along the downstream . 
Options: a ) 4 hrs . , b ) 1 hrs . , c ) 3 hrs . , d ) 2 hrs . , e ) 2 1 / 2 hrs .

Ex Output:

d