A monopoly with constant marginal cost of $50 can sell to three groups of potential consumers, with demand Q1 = 800 - 0.2p, Q2 = 400 - p, and Q3 = 700 - 0.4p, respectively. Find the optimal price-quantity combination in the market.

i) if the firm is able to price-discriminate

ii) if it is not able to price-discriminate