Firm A: P = MR = MC and ATC > P > AVC.
Firm B: P > MR = MC and P = ATC > AVC.
Firm C: P > MR = MC and P > ATC > AVC.
Firm D: P = MR < MC and ATC > P > AVC.
Firm E: P = MR > MC and P = ATC > AVC.
Firm F: P > MR > MC and P > ATC > AVC.
Of the six firms portrayed above, which are operating as perfectly competitive, price-taking ones? Briefly defend (or comment upon) your response.