A complicated calculation

The figure above depicts the so-called great rhombicuboctahedron, it has $26$ faces: $6$ regular octagons, $8$ regular hexagons, and $12$ squares, all of the same edge length. If the edge length is $1$ , find the volume of the polyhedron. The volume can be expressed as $a + b \sqrt{2}$ for positive integers $a , b$ . Enter $a + b$