1/8 a^{v0,v1}_{c1,c2} b^{c0}_{a0} c^{c1,c2}_{a1,a2} a+(a0) a+(a1) a+(a2) a-(v1) a-(v0) a-(c0)
-1/4 a^{v0,v1}_{c1,c2} b^{c1}_{a0} c^{c0,c2}_{a1,a2} a+(a0) a+(a1) a+(a2) a-(v1) a-(v0) a-(c0)