4. In general a firm's (LO2) a) total cost rises as output rises up to a certain point and then begins to decline b) marginal cost rises as output rises up to a certain point and then begins to decline c) average total cost declines as output rises up to a certain point and then begins to rise 5. If AVC is declining, then (L05) a) marginal cost must be less than AVC b) marginal cost must be greater than ATC c) AVC must be greater than AFC