Your help is greatly appreciated! Thank you for your time.

(1 point) Check that the point (4, 4, 2) lies on the surface cos(x + y) = exz'fs. (a) View this surface as a level surface for a function f(x, y, z). Find a vector normal to the surface at the point (4, 4, 2). (b) Find an implicit equation for the tangent plane to the surface at (4, 4, 2)