Monopolist engaging in international trade
Because the monopolist is only a monopolist in its own country, it is basically in perfect competition in the international market and cannot influence the world price. Therefore, it will have to use the condition that price is equal to marginal cost. His marginal cost (MC) is the first derivative of total cost, i.e. TC'=2Q=MC. If MC=P, then 2Q=10. Therefore, Q=5. 

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