Determine if the statements below are true or false. (a) if f · da s = 12 and s is a flat disk of area 4π, then divf = 3 π . true false (b) if f is a vector field in 3-space, then grad(divf) = 0 i + 0 j + 0 k true false (c) if s is the unit sphere oriented outward and f is a vector field satisfying f · da s = 0 , then divf = 0 at all points inside s.