A \(60-\mathrm{kg}\) person jumps off a chair and lands on the floor at a speed of \(1.2 \mathrm{~m} / \mathrm{s}\). Once his feet touch the floor surface, he slows down with constant acceleration by bending his knees. During the slowing down, his center of mass travels \(0.25 \mathrm{~m}\). Determine the magnitude of the force exerted by the floor surface on the person and the work done by this force on him.