7. (20 points, 4 each part, graded on completion) Paddy's Pub is a profitmaximizing bar in Philadelphia that sells bottles of beer. They have three major expenses: they have to pay their rent, they have to buy beer to sell to customers, and they have to buy glass bottles to put the beer in. The customers of Paddy's Pub are a rowdy lot, and smash the glass bottles after using them. (With this problem: In general, the economies are more important than the math. Feel free to use online tools to get past the trickier math parts.) (a) In the short run, which of these expenses are xed costs? Which of these expenses are variable costs