import cadquery as cq
w0=cq.Workplane('XY',origin=(0,0,21))
w1=cq.Workplane('ZX',origin=(0,2,0))
r=w0.workplane(offset=-71/2).moveTo(0,8).box(12,28,71).union(w1.sketch().push([(7.5,0)]).rect(85,30).push([(-30,2)]).rect(8,8,mode='s').finalize().extrude(-24))