Find (a) the grad and (b) the unit vector normal to the surface xy - yz +3xz = 2y -1 at (-1, 3, - 2). Show that div(Vxu)=0. 3. 4. The force acting on a particle located at the point (x,y.z) is F = xyi,-(z-y)i, +2xi,. Find the work done when the particle moves along the curve x =t, y =t, z =t from point (-1, 1,-1) to (3, 9, 27). 5. Show that if a vector is irrotational, then it is the gradient of a scalar point 2.