Example 9.5.2 (Application of the Graph Coloring Heuristic). Gary, Hamilton, Izak and Reha are university professors attending a national conference. During this conference seven one hour meetings have to be scheduled in such a way that each one of the four professors can be present at all the meetings he has to attend. The goal is to schedule all seven meetings in a single afternoon between 2 p.m. and 6 p.m