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: two taps a and b can fill a cistern in 12 minutes and 18 minutes respectively . they are turned on at the same time . if the tap a is turned off after 4 minutes , how long will tap b take to fill the rest of the cistern ? 
Options: a ) 8 min . , b ) 9 min . , c ) 10 min . , d ) 7 min . , e ) none of these

Ex Output:
a


Ex Input:
Problem: i flew my tiny seaplane to visit my mother . on the flight up , i flew at 110 mph . on the way home , i flew 90 mph . what was my average speed for the trip ? 
Options: a ) 198 mph , b ) 110 mph , c ) 88 mph , d ) 100 mph , e ) 99 mph

Ex Output:
d


Ex Input:
Problem: a train 800 m long can cross an electric pole in 20 sec and then find the speed of the train ? 
Options: a ) 87 kmph , b ) 97 kmph , c ) 72 kmph , d ) 144 kmph , e ) 120 kmph

Ex Output:

d