Partial derivative

3. (15 points) (A) Let f ( x, y, z) = ( x2 + y 2 + 2 2 ) - 2 + In(xyz). Find the rate of change of f along u = (3, 4, 5) at point (-1, 2, -2). (B) Find the parametric equations of the tangent plane T to the level surface S : f (x, y, z) = = + In4 at (-1, 2, -2), where f(x, y, z) is given in (A). Also, find the normal line of the level surface S at (-1, 2, -2)