A1Bottom level first position from front end. A2Bottom level second position from front end. A3Bottom level third position from front end. A4Bottom level fourth position from front end A5Bottom level fifth position from front end. A6Bottom level sixth position from front end. A7Bottom level seventh position from front end B1Second level first position from front end. B2Second level second position from front end. B3Second level third position from front end. B4Second level fourth position from front end. B5Second level fifth position from front end. B6Second level sixth position from front end. B7Second level seventh position from front end. C1Third level first position from front end. C2Third level second position from front end. C3Third level third position from front end. C4Third level fourth position from front end. C5Third level fifth position from front end. C6Third level sixth position from front end. C7Third level seventh position from front end.