A device for measuring compressibility consists of a cylinder filled with oil and fitted with a piston at one end. A block of sodium is immersed in the oil, and a force is applied to the piston. Assume that the piston and walls of the cylinder are perfectly rigid and that there are no friction and no oil leak. Compute the compressibility of the sodium in terms of the applied force F, the piston displacement x, the piston area A, the initial volume of the oil Vo, the initial volume of the sodium Vs, and the compressibility of the oil ko.