An 80 kg man stands at the edge of a horizontal circular platform having a moment of inertia of 720 kgm-2 and a radius of 2 m.  The platform is initially at rest and is free to rotate about a frictionless, vertical axel through its centre.  The man then starts walking around the edge clockwise (as viewed from above) at a speed of 1.5 m/s relative to the earth then the work done by the man is