RJuan and Sylvester are collaborating on a group project for a class but are having trouble agreeing on objectives and goals. Their professor senses the trouble they are having and steps in to help them refine their goals and come to an agreement. The professor assumed which of Georg Simmel's roles?

mediator

Explanation: Mediator refers to an unbiased individual who gets involved on issues or conflicts between two or more people with the aim of resolving or quelling the trouble. The mediator may be an older or more experienced individual in the field or subject of discussion which can enlighten the conflicting parties and proffer adequate solution. In the context above, the professor assumed the role of a mediator.