(3) [Marked] Consider the surface of revolution = {(x,y (x, y, z) € R³ | x² + z² *-{\306842-({+1})} H = = cos (a) Find the tangent plane to H at (23/2,π, -23¾½). (See also (Q7) of Problem Sheet 7.) (b) Find the unit normals to H at (23/2, π, 2√2 (2√21π-232). (c) Which of the two unit normals in (b) represents the "outward-facing" side of H? (For part (c), you do not have to prove the answer. You can find the answer by sketching H and the appropriate normals and then inspecting your sketch.)