Final answer:
To find the long-run equilibrium output and selling price for companies A and B, we need to calculate their maximum profits and use the demand function to determine the equilibrium selling price. By plugging in the equilibrium quantities into the revenue and cost functions, we can find the total profits for each company and the total industry profits.
Step-by-step explanation:
To find the long-run equilibrium output and selling price for companies A and B, we need to find the quantities at which their profits are maximized. In a Cournot duopoly model, each firm assumes that the other firm's output will not change.
For company A, we can find the equilibrium output by maximizing its profit function, which is given by P(A) * QA - TC(A). Taking the derivative of this function concerning QA and setting it equal to zero, we can solve for QA. Similarly, we can find QB for company B.
Once we have the equilibrium quantities, we can plug them into the demand function to find the equilibrium selling price. The total profits for each company can be calculated by subtracting the total cost function from the revenue function at the equilibrium output.
Using these calculations, we can determine the long-run equilibrium output and selling price for companies A and B, as well as their total profits and the total industry profits.