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: noelle walks from point a to point b at an average speed of 6 kilometers per hour . at what speed , in kilometers per hour , must noelle walk from point b to point a so that her average speed for the entire trip is 7 kilometers per hour ?
Options: a ) 6.75 , b ) 7 , c ) 7.25 , d ) 7.5 , e ) 8.4

Ex Output:
e

Ex Input:
Problem: a boat covers a certain distance downstream in 1 hour , while it comes back in 1 hours . if the speed of the stream be 3 kmph , what is the speed of the boat in still water ?
Options: a ) 12 kmph , b ) 13 kmph , c ) 14 kmph , d ) 15 kmph , e ) none

Ex Output:
d

Ex Input:
Problem: 6 boysand 8 girls can do job in 10 days , 26 boys & 48 women do work in 2 days find time taken by 15 boys and 20 girls to do same work
Options: a ) 4 days , b ) 5 days , c ) 6 days , d ) 7 days , e ) 8 days

Ex Output:
a