A pizza business has the cost structure described in the table. The firm's fixed costs are $20 per day. Output (pizzas per day) Total cost of output (fixed + variable) 10 $20 15 $80 10 $120 15 $150 20 $175 25 $195 30 $210 35 $230 $255 40 What are the firm's average fixed costs at an output of five pizzas? $4 $20 $80 O $100