Consider the expression X = 3x4 10x3 69x2 + 264x 80. (a) Show that c1 = 5, c2 = 1/3, and c3 = 4 are critical numbers of X (you can use a calculator if necessary). (b) Assuming that c1, c2, and c3 are the only critical numbers of X, determine the solution set when X > 0.