A company can successfully charge different prices in country A and B. Marginal cost is $10. Demands in country A and B are Q=20.5-P and Q=5-P respectively. What are the profit- maximising prices in two countries? What quantity do they sell in two countries?

The company now added country C, and its demand is Q=20.5-P. What maximising prices do they charge in three countries? What quantity do they charge in three countries?