3. (2 pts.) Find fc F. dr for F = (x^y-7x+1, 5+y9-7) and C the unit square traversed counter clockwise ( along the line segments (0,0) (1,0) (1,1) (0, 1) (0,0)). 4. (2 pts.) For (a) assume f(x, y) is some differentiable function. For (b), assume H = (h1, h2, h3) is differentiable vector field. (a) Show that if F(x, y) = f(x, y), then curl(F) = 0. (b) Show that if (x, y, z) = curl(x, y, z), then div(G) =