1-Edge contraction: Total vertex stress and confluence number

This paper introduces certain relations between $1$-edge contraction and the total vertex stress and the confluence number of a graph. A main result states that if a graph $G$ with $\zeta(G)=k\geq 2$ has an edge $v_iv_j$ and a $\zeta$-set $\mathcal{C}_G$ such that $v_i,v_j\in \mathcal{C}_G$ then, $\zeta(G/v_iv_j) = k-1$. In general, either $\mathcal{S}(G/e_i) \leq \mathcal{S}(G/e_j)$ or $\mathcal{S}(G/e_j) \leq \mathcal{S}(G/e_i)$ is true. This observation leads to an investigation into the question: for which edge(s) $e_i$ will $\mathcal{S}(G/e_i) = \max\{\mathcal{S}(G/e_j):e_j \in E(G)\}$ and for which edge(s) will $\mathcal{S}(G/e_j) = \min\{\mathcal{S}(G/e_\ell):e_\ell \in E(G)\}$?