​A firm's sunk costs are $100,000 and its marginal costs are $250 per unit.It produces 500,000 units and prices it at $400 per unit. ,How low can price go before the firm decides to shut down?

A) ​$150
B) $250
C) $250.20
D) ​$400

If you eat at a Las Vegas casino that charges $12 for its all you can eat buffet, then the marginal cost of your third trip to the buffet line is

A) zero.
B) $4.
C) $12.
D) $36.