1/4 a^{a1}_{c0,c1,a0} b^{c4}_{c2,c3,a2} eta1^{a2}_{a1} a+(c0) a+(c1) a+(c2) a+(c3) a+(a0) a-(c4)
+1/2 a^{a1}_{c0,c3,a0} b^{c3}_{c1,c2,a2} a+(c0) a+(c1) a+(c2) a+(a0) a+(a2) a-(a1)
-1/2 a^{a1}_{c0,c3,a0} b^{c3}_{c1,c2,a2} eta1^{a2}_{a1} a+(c0) a+(c1) a+(c2) a+(a0)