Final answer:
Manager Dongfang acted in an interpersonal role when resolving the disagreement between two baristas, which involves conflict resolution and maintaining workplace harmony.
Step-by-step explanation:
When Dongfang, the manager at Common Grounds Coffee, had to diffuse a disagreement between two baristas, he was acting in a managerial role that could be categorized as the interpersonal role. This role entails tasks such as conflict resolution, team leadership, and maintaining workplace harmony, which are critical to managing difficult work relationships and work overload. Managers often need to be versatile, sometimes requiring them to act as a mediator in order to address and resolve interpersonal conflicts among employees, thereby ensuring a cohesive and effective work environment.