A complete tripartite K r,s,t is a generalization of a complete bipartite graph. There are three subsets of vertices, r in teh first subset, s in the second subset, and t in the third subset. Every vertex in one particular subset is adjacent to every vertex in the other two subsets; that is, a vertex is adjacent to all vertices except those in its own subset. Determine all the triples r,s,t for which K r,s,t is planar. I am thinking that there must be a minium of 12 vertices....But I am not sure... . . . . . . . . Maybe two side by side and one underneath? I am not sure . . . .