Five objects, each of mass M, are equally spaced on the arc of a semicircle of radius R as shown. An object of mass m is located at the center of curvature of the arc. (a) If M is 3.0 kg, m is 2.0 kg, and R is 10 cm, what is the gravitational force on the particle of mass m due to the five objects? (b) What is the gravitational potential energy of mass m?