1. As shown in the figure, two circular hole of radiusr was excavated from a uniform circular disc of mass M, radius R. The centers of two holes are in the midpoints of radius. Find the moment of inertia of the remaining part about the axis which is perpendicular to the circular disc through its center. R 2. Two ice skaters move in two parallel lines in opposite directions. The mass and velocity of the two skaters are: ma=60 kg, mg=70 kg, vA=7m/s, V8-6m/s. When they are getting closest to each other, they hold hands and begin circular motion about the center of mass and their distance is 1.5m. Find (a) The total angular momentum of the two skaters about the center of mass and the angular velocity of the two skaters; (b) The total kinetic energy of the two skaters before and after holding hands. Is mechanical energy conserved during this process?