3. Find a field F(x, y) = (M(x, y), N(x, y) ) in the xy-plane with the property that at each point (x, y) # (0, 0), F is a unit vector pointing toward the origin. (The field is undefined at (0, 0).) 4. Is the vector field F(x, y, z) = (yz, xz, xy) conservative? Justify your