Solve the below problem:
Q: You cast some metal of density Pm in a mold, but you are worried that there might be cavities wit13in the casting. You measure the weight of the casting to be w, and the buoyant force when it is completely surrounded by water to be B.
(a) Show that Vo = B/(P water g) - w/(P m g) is the total volume of any enclosed cavities.
(b) If your metal is copper, the casting's weight is 156 N, and the buoyant force is 20 N, what is the total volume of any enclosed cavities in your casting? What fraction is this of the total volume of the casting?