To calculate the firm's economic profit, we need to determine the total revenue (TR), total cost (TC), and then find the difference between them.

Total Revenue (TR): Total revenue is calculated as price (P) multiplied by quantity (Q).

=TR=PQ

From the previous answers, we have =70P=70 and =3000Q=3000.

=703000=210,000TR=703000=210,000

Total Cost (TC): Total cost is calculated as average total cost (ATC) multiplied by quantity (Q). Given that ATC is constant at $40:

=TC=ATCQ

=403000=120,000TC=403000=120,000

Economic Profit: Economic profit is the difference between total revenue and total cost.

EconomicProfit=EconomicProfit=TRTC

EconomicProfit=210,000120,000=90,000EconomicProfit=210,000120,000=90,000

Therefore, the firm's economic profit at the current quantity traded is $90,000.