2. Let G be a graph.
(a) State a bound on x(G) in terms of the maxi- mum degree of G.
(b) If x(G) = 2, show that G has no cycle of length 3.
(c) For a natural number k, explan what the function x(G, k) counts.
(d) Determine x(Kn, k), and use your formula to show that x(Kn) = n.
