2. (Two points) Let I be a directed graph and -T be the same graph with opposite directions on all edges. Prove that their 2-variable degree polynomials Dr(r, s) and D-r(r, s) are related by D-r(r, 8) = Dr(s,r). 2. (Two points) Let I be a directed graph and -T be the same graph with opposite directions on all edges. Prove that their 2-variable degree polynomials Dr(r, s) and D-r(r, s) are related by D-r(r, 8) = Dr(s,r)