The average value of a function f(x, y, z) over a solid region e is defined to be fave = 1 v(e) e f(x, y, z) dv where v(e) is the volume of e. for instance, if ρ is a density function, then ρave is the average density of e. find the average value of the function f(x, y, z) = 3x2z + 3y2z over the region enclosed by the paraboloid z = 9 − x2 − y2 and the plane z = 0.