Country a Has the Following Constant-Opportunity-Costs Production-Possibilities Frontier (PPF)

Country A has the following constant-opportunity-costs production-possibilities frontier (PPF) :

Suppose that this country in autarky is located at point R on its PPF, where it is producing 300 units of good Y and __________ of good X. Suppose that country A is now opened to trade and can trade at a terms of trade of 1X:3Y. Assuming complete specialization in production, the country will now produce at __________.

A) 50 units; point N and will export good X and import good Y
B) 150 units; point N and will export good X and import good Y
C) 50 units; point M and will export good Y and import good X
D) 150 units; point M and will export good Y and import good X