How do i find the centre of mass in a circular shape on COMSOL?

Hi,

I have a circle of radius 40mm extruded to a height of 4mm and divided into 8 equal parts or domains.

1. How do I retrieve the (centre of mass) for this shape on COMSOL?

2. How do i know the x, y and z coordinates of any point in this shape on COMSOL?

Thanks