(b) Consider 2 consumers A and B of a product with individual demand functions QA = 400 - 5PA and QB = 300 - 2PB, respectively. (i) If the product is a private good, analyse the market and solve for the optimal quantity if the marginal cost is $10. How will your answer be different if the marginal cost is $90? (ii) If the product is a public good, analyse the market and solve for the optimal quantity if the marginal cost is $10? How will your answer be different if the marginal cost is $90?