A bipartite graph is a graph in which the vertices can be divided into two disjoint nonempty sets A and B such that no two vertices in A are adjacent and no two vertices in B are adjacent. The complete bipartite graph Km,n is a bipartite graph in which |A| = m and |B| = n, and every vertex in A is adjacent to every vertex in B.

(a) Sketch K3,2.

(b) How many edges does Km,n have?

(c) For which m and n does Km,n have an Euler circuit?