Consider a vector field, F(r,theta,phi)= ar*cos^2(theta)/r^2 for the volume V of a spherical shell, centered at the origin,with inner and outer radii 1 and 2 meters. a) Evaluate triple integral delta.F dv over v. b) Calculate also the closed surface F.ds and verify the divergence c) Can F be expressed as the curl of a vector? explain.