A person of mass \(m=67 \mathrm{~kg}\) stands on a boat of mass \(M=420 \mathrm{~kg}\). The boat can move, without friction, on the surface of a calm lake. The system is initially in equilibrium. The person starts walking on the boat in the right direction, with a constant speed \(v=4.0 \mathrm{~km} / \mathrm{h}\) with respect to the boat. What is the relative speed \(V\) of the boat with respect the lake? What is the speed \(v^{\prime}\) of the person with respect to the lake?