For parts (c) and (d), now consider that m is less than, but comparable to, M. Both objects now circle their common center of mass; the mass M makes a circular orbit of radius R about the CM, and the mass m makes a radius r as shown. J (c) (2 points) Write an equation that relates M, m, R, and r. CM R MR = mr D (d) (4 points) Derive an expression for the orbital speeds Um and UM of the mass m and the mass M respectively. Express your answers in terms of M, m, r, R, and fundamental constants