The diagram shows a mass, M, starting at point A with a spee…

The diаgrаm shоws а mass, M, starting at pоint A with a speed vо.  The mass moves along a path that includes a hill of height, h, a valley of height –h/2, and when it reaches point B, which is at the same height as point A, it has a speed, v = 0.5vo.  Which of the following expressions correctly corresponds to the work done by an external force (Fext)?