Evaluate the surface integral Th F⚫ds for the given vector field F and the oriented surface S. In other words, find the flux of F across S. For closed surfaces, use the positive (outward) orientation. F(x, y, z) = -xi - yj + z³k, S is the part of the cone z = √√x² + y² between the planes z = 1 and z = 4 with downward orientation ZA z = √x²+ y² xx z=4