Which of the following is correct about a perfectly competitive firm? O A. O B. O c. If price is lower than average variable cost, it will shut-down and incur fixed costs If price is lower than average total cost, it will exit and incur fixed and variable costs If price is lower than average variable cost, it will exit and incur fixed costs O D. If price is lower than average total cost, it will shut-down and incur fixed and variable costs