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 3 kilometers per hour . it returns by the same route at an average speed of 7 kilometers per hour . what is the average speed for the round - trip in kilometers per hour ? 
Options: a ) 4.2 , b ) 7.1 , c ) 7.2 , d ) 7.5 , e ) 8.0

Ex Output:
a


Ex Input:
Problem: a fill pipe can fill 2 / 3 of cistern in 40 minutes in how many minutes , it can fill full of the cistern ? 
Options: a ) 60 min , b ) 36 min , c ) 25 min , d ) 30 min , e ) 50 min

Ex Output:
a


Ex Input:
Problem: 42 persons can repair a road in 12 days , working 5 hours a day . in how many days will 30 persons , working 6 hours a day , complete the work ? 
Options: a ) 10 , b ) 16 , c ) 13 , d ) 14 , e ) 19

Ex Output:

d