Task: Question Answering
Input (English): Problem: noelle walks from point a to point b at an average speed of 3 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 4 kilometers per hour ? 
Options: a ) 5.75 , b ) 6 , c ) 7.25 , d ) 7.5 , e ) 7.75
Output (English): b