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 river boat leaves silver town and travels upstream to gold town at an average speed of 6 kilometers per hour . it returns by the same route at an average speed of 5 kilometers per hour . what is the average speed for the round - trip in kilometers per hour ? 
Options: a ) 5.5 , b ) 7.1 , c ) 7.2 , d ) 7.0 , e ) 8.0

Ex Output:
a


Ex Input:
Problem: a train passes a station platform in 20 sec and a man standing on the platform in 12 sec . if the speed of the train is 72 km / hr . what is the length of the platform ? 
Options: a ) 227 , b ) 140 , c ) 160 , d ) 120 , e ) 171

Ex Output:
c


Ex Input:
Problem: in what time will a train 320 m long cross an electric pole , it its speed be 144 km / hr ? 
Options: a ) 2.5 sec , b ) 8.0 sec , c ) 3.5 sec , d ) 2.9 sec , e ) 9.5 sec

Ex Output:

b