-1/4 a^{c0,a3}_{a0,a1} b^{c1,c2}_{c3,a2} c^{c3}_{a4} eta1^{a4}_{a3} a+(a0) a+(a1) a+(a2) a-(c2) a-(c1) a-(c0)
+1/4 a^{c0,a3}_{a0,a1} b^{c1,c2}_{c3,a4} c^{c3}_{a2} eta1^{a4}_{a3} a+(a0) a+(a1) a+(a2) a-(c2) a-(c1) a-(c0)