Final answer:
The priority action is to notify the healthcare provider because this may indicate postpartum hemorrhage.
Step-by-step explanation:
The priority action for a patient with a firm fundus who is saturating a pad in 50 minutes is d) Notify the healthcare provider. This situation may indicate postpartum hemorrhage, which is a serious complication. Prompt notification of the healthcare provider is necessary to ensure appropriate medical intervention. The patient's vital signs should also be monitored closely while waiting for the healthcare provider's arrival.