3. A walk around Königsberg which would cross each of the seven bridges exactly once is equivalent to an Euler path. Recall that an Euler path from v to w is a sequence of adjacent edges and vertices that starts at v, ends at w, passes through every vertex of G at least once, and traverses every edge of G exactly once. To answer this question, use Corollary 11.2.5 which states that that there is an Euler path from v to w in G if, and only if, G is connected, v and w have odd degree, and all other vertices have even degree.