In this task, you need to answer the given multiple-choice question on the general math. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Ex Input:
Problem: a cyclist rides a bicycle 7 km at an average speed of 10 km / hr and again travels 10 km at an average speed of 7 km / hr . what is the average speed for the entire trip ? 
Options: a ) 7.59 , b ) 7.79 , c ) 7.99 , d ) 8.19 , e ) 8.39

Ex Output:
c


Ex Input:
Problem: 8597 - ? = 7429 - 4358 
Options: a ) 3567 , b ) 6424 , c ) 6835 , d ) 5526 , e ) none of these

Ex Output:
d


Ex Input:
Problem: a man has some hens and cows . if the number of heads be 48 and the number of feet equals 140 , then the number of hens will be : 
Options: a ) 43 , b ) 26 , c ) 33 , d ) 21 , e ) 28

Ex Output:

b