Question: 1. Explain why there is always an ordering of the vertices for which the greedy algorith m will lead to a colouring with X(G) colours.
2. Find the chromatic index of each of the five Platonic solid graphs.
3. A graph in which every vertex degree is 3 is called a cubicgraph. Prove that all hamiltonian cubic graphs have chromatic index 3. (Note however that not all cubic graphs have chromatic index 3. e.g. the Petersen graph.)