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: calculate the speed of a boat in still water ( in km / hr ) if in one hour , the boat goes 10 km / hr downstream and 4 km / hr upstream . 
Options: a ) 7 kmph , b ) 8 kmph , c ) 9 kmph , d ) 7 kmph , e ) 6 kmph

Ex Output:
a


Ex Input:
Problem: the length of the bridge , which a train 130 meters long and travelling at 45 km / hr can cross in 30 seconds , is ? 
Options: a ) 288 , b ) 266 , c ) 245 , d ) 277 , e ) 211

Ex Output:
c


Ex Input:
Problem: in how many seconds will a train 180 meters long pass an oak tree , if the speed of the train is 54 km / hr ? 
Options: a ) 10 , b ) 12 , c ) 14 , d ) 16 , e ) 18

Ex Output:

b