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