4. Joe and his brother Bo have a combined mass of 200.0 kg and are zooming along in
a 100.0 kg amusement park bumper car at 10.0 m/s. They bump into Melinda's car,
which is sitting still. Melinda has a mass of 25.0 kg. After the collision, the twins
continue ahead with a speed of 4.12 m/s. How fast is Melinda's car bumped across
the floor?