-1/2 a^{}_{c0,c4,a0} b^{c3,c4}_{c1,c2} a+(c0) a+(c1) a+(c2) a+(a0) a-(c3)
+1/4 a^{}_{c2,c3,a0} b^{c2,c3}_{c0,c1} a+(c0) a+(c1) a+(a0)