In a certain binary star system, two stars with identical mass m have equal and opposite velocities v2 on the opposite sides of the same circular orbit with radius R. In another system with three identical stars of the same mass m as before, it is observed that all three stars are equally spaced around a circular orbit with the same radius R as before. What is the speed v3 of these stars in terms of u? [Hint: consider the direction and magnitude of the force exerted on one star by the other two.] [9]