How fast did it move after the collision?

A 2000 lb. Mazda Miata is going 39.0 miles per hour (mph) and it runs into a stationary 8000 lb. SUV. After the collision, both vehicles stick together. If the wheels continue to rotate freely so that there is no frictional force of the road on the vehicles, how fast is the combined SUV-Miata blob moving right after the collision? Explain your response.