How to #9

The three spheres in the figure, with masses ma = 83 g, mg = 10 grand mc = 23 g, have their centers on a common line, with L = 23 cm and d = 4 cm. You move sphere B along the line until its center-to-center separation from Cisd = 4 cm. How much work is done on sphere B(a) by you and (b) by the net gravitational force on B due to spheres A and C? B A