A monopoly with constant marginal costs of $50 can sell to three groups of potential consumers, with demands Q1 = 800 - 0.2p, Q2 = 400 - p, and Q3 = 700 - 0.4p respectively. Find the optimal price- quantity combination in each market
(i) if the firm is able to price-discriminate;
(ii) if it is not able to price-discriminate.