-1/2 a^{a0}_{c2} b^{c2,a2}_{c0,c1} c^{a1}_{a3} eta1^{a3}_{a2} a+(c0) a+(c1) a-(a1) a-(a0)
+1/2 a^{a2}_{c2} b^{c2,a0}_{c0,c1} c^{a1}_{a3} eta1^{a3}_{a2} a+(c0) a+(c1) a-(a1) a-(a0)