Cloud Kicks has been tracking how many participants wear the company's shoes in each marathon. The administrator creates two custom objects: Races and Runners. There is a master-detail relationship between them as well as a Roll-up Summary field on the Races object to show the count of runners in each race. Requirements have changed, and the administrator wants to delete the Master-detail Relationship field without deleting the Runners records.

What action should an administrator take before the Relationship field can be deleted?