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