c) If demand shifts to the left (i.e., Qd decreases for every price), the last firm that entered: A. is indifferent between producing or exiting the market and so the outcome is indeterminate. B. earns negative economic profits and thus undertakes cost-cutting measures to return to profitability. C. earns positive economic profits, leading to new firms entering the market. D. earns negative economic profits and so exits the market