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'.

Example 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
Example Output: d

Example Input: Problem: two trains of length 100 meters and 200 meters are 840 meters apart . they are moving towards each other on parallel tracks , at speeds of 54 km / h and 72 km / h . after how many seconds will the trains meet ? 
Options: a ) 20 , b ) 22 , c ) 24 , d ) 26 , e ) 28
Example Output: c

Example Input: Problem: if an object travels at nine feet per second , how many feet does it travel in one hour ? 
Options: a ) 30 , b ) 300 , c ) 720 , d ) 1800 , e ) 32400
Example Output:
e