How would you determine the firm's level of output and decision to shut down or continue operating in the short run when facing a market price of 100, given the firm's total cost of 5000 and average fixed cost of 20? A) Market price: 150 Total cost: 6000 Average fixed cost: 30 B) Market price: 80 Total cost: 4000 Average fixed cost: 25 C) Market price: 100 Total cost: 4000 Average fixed cost: 40 D) Market price: 120 Total cost: 6000 Average fixed cost: 35