Looking ahead- tangent planes Consider the following surfaces $f(x, y, z)=0,$ which may be regarded as a level surface of the
function $w=f(x, y, z) .$ A point $P(a, b, c)$ on the surface is also given.
a. Find the (three-dimensional) gradient of $f$ and evaluate it at $P$.
b. The set of all vectors orthogonal to the gradient with their tails at $P$ form a plane. Find an equation of that plane (soon to be called the tangent plane).
$$f(x, y, z)=8-x y z=0 ; P(2,2,2)$$