A large business, with several medical practices, contacted your company to create a database design. You received the task to investigate if there is a need for a hierarchy based on the specifications below, and to create the hierarchy analysis if needed. You must not create the entire analysis but only the aspects related to the hierarchy as described in the instructions, class lectures and sample examples. This is the relevant fragment from the requirements specification related to your task. In the practice we have medical doctors, staff and other employees (e. g. cleaners for which we just keep contact information: name, SSN, phone). For the doctors we keep the name, SSN, phone, email, main specialty, medical school. A doctor may have appointments and write prescripions. For staff we keep the name, SSN, phone and their role (e. g. receptionist, scheduler, accountant). Based on the practice policies, some doctors are allowed to perform staff duties for a given role as needed. The company wants to keep a log with who was working daily, between what hours and in which role. The company also wants to fast identify the role of a person in the organization (e. g. doctor, staff, ...), based on the last name or id.