Use Stokes' theorem to evaluate the work done by the force field F=((f(x,y,z),6xy,x+yz), where f:R3R is an arbitrary smooth function, while moving an object first from the point (2,1,0) to the point (2,1,0) along the semi-circle (with z0 ) of radius 1 in the plane x=2 , and then back to the point (2,1,0) along the line x=2 in the (x,y) -plane