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 can do a piece of work in 4 hours ; b and c together can do it in 2 hours , while a and c together can do it in 2 hours . how long will b alone take to do it ? 
Options: a ) 12 , b ) 9 , c ) 8 , d ) 6 , e ) 4

Ex Output:
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: machine a takes 20 hours to complete a certain job and starts that job at 6 am . after four hour of working alone , machine a is joined by machine b and together they complete the job at 1 pm . how long would it have taken machine b to complete the job if it had worked alone for the entire job ? 
Options: a ) 9.99 , b ) 3,615 , c ) 3.62 , d ) 4.62 , e ) 6.14

Ex Output:

d