I'm struggling in this question. Please help me explain, thank you so much!

Question Set Five: 4. Pinnacle Paper Products Inc. can produce books or rolls of paper towels. Here is its PPF for the resources and technology it has available: 620 - 610 B 590 540 485 E Rolls of Paper Towels 380 220 20 50 60 Books What is the opportunity cost of choosing to produce at point B, instead of at point A? What is gained by choosing to produce at point C, instead of at point B? 5. Douglas Fur is a small manufacturer of fake-fur boots in New York City. The following table shows the company's total cost of production at various production quantities. Fill in the blanks. Cost schedule Quantity Total Cost Marginal Cost Fixed Cost Variable Cost Average Variable Cost Average Total Cost (Pairs) (Dollars) (Dollars) (Dollars) (Dollars) (Dollars per pair) (Dollars per pair) 0 50 160 220 W 270 A 340 450 630