Task: Question Answering
Input (English): Problem: a car traveling at a certain constant speed takes 2 seconds longer to travel 1 kilometer than it would take to travel 1 kilometer at 900 kilometers per hour . at what speed , in kilometers per hour , is the car traveling ? 
Options: a ) 671.5 , b ) 600 , c ) 672.5 , d ) 673 , e ) 773.5
Output (English): b