Solve the Integral in cylindrical coordinates

∫∫∫ dxdydz/(sqrt( x^2 + y^2 + (h-z)^2)

B

Where B is the Ball with a Radius R around (0,0,0), and the parameter h is greater than R.

And then infer the average on that ball B with radius R of the distance opposite to the point (0,0,h)

(the average of function f on some shape v is defined as

[ ∫∫∫ f(x,y,z) dxdydz ] / vol V

v