(a) There are 13 European cities that Joe would eventually like to visit. On his next vacation, though, he only has time to visit 3 of the cities: one on Monday, one on Tuesday, and one on Wednesday. He is now trying to make a schedule of which city he'll visit on which day. How many different schedules are possible? (Assume that he will not visit a city more than once.) (b) A pizza parlor has a choice of 11 toppings for its pizzas. From these 11 toppings, how many different 8-topping pizzas are possible? >