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: a car gets 40 kilometers per gallon of gasoline . how many gallons of gasoline would the car need to travel 210 kilometers ? 
Options: a ) 8.25 gallons , b ) 7.5 gallons , c ) 6.55 gallons , d ) 5.25 gallons , e ) 4.5 gallons

Ex Output:
d


Ex Input:
Problem: train a leaves the station traveling at 30 miles per hour . two hours later train в leaves the same station traveling in the same direction at 36 miles per hour . how many miles from the station was train a overtaken by train b ? 
Options: a ) 320 , b ) 360 , c ) 400 , d ) 440 , e ) 480

Ex Output:
b


Ex Input:
Problem: a , b and c can do a piece of work in 7 days , 14 days and 28 days respectively . how long will they taken , if all the three work together ? 
Options: a ) 4 , b ) 3 , c ) 5 , d ) 2 , e ) 1

Ex Output:

a