A 50 kg person stands at the edge of a 7.4 m diameter circular platform, which is mounted horizontally on frictionless bearings and has a total mass of 300 kg. The platform is at rest initially, but when the person begins running at a speed of 10 m/s (with respect to the platform) around its edge, the platform begins to rotate in the opposite direction. What is the magnitude of the speed of the person (in m/s) with respect to the ground? You can model the platform as a circular disk.