The weightless horizontal bar in the figure below is in equilibrium. Scale B reads 4.15 kg. The distances in the figure (which is not to scale) are: D1 = 6.5 cm, D2 = 10.0 cm, and D3 = 5.0 cm. The mass of block X is 0.94 kg and the mass of block Y is 2.04 kg. Determine what the reading on scale A must be. I am not sure where to start with this problem.