Work, Gravity, and Friction

(1) Determine the work done by the frictional force in moving a block of mass m from point 1 to point 2 over the two paths (a) and (b) shown in the figure below. The coefficient of friction has the constant value µ over the surface and the diagram lies in a horizontal plane.

(2) Assume the figure above lies in a vertical plane, and find the work done by the gravitational force as an object moves from point 1 to point 2 over each of the paths shown.