Workflow: Send notifications to group that reviewer belongs to

I am creating a workflow.  In the workflow, I select a reviewer and the Department.  I have a property called 'Department' with value list that has the departments.

The workflow ends with sending a notification to the department (i.e.,  How can I find in the metadata the reviewer belongs to?  The reviewer belongs to a User Group that is the same name as the Department.

Please assist.  Thanks.