Show why the (p, q) combinations (4, 4), (4, 5), (5, 4), and (5, 5) are ruled out for regular maps. 5. Find formulas for f, v, and e in terms of p and q that hold for the regular maps. 6. (a) Show that if two pentagons ABCDE and A′B′C′D′e′ are both...