Database Design 1: ProjectDB (20 points) A company has a number of employees. The attributes of EMPLOYEE include Employee_ID (identifier), Name, Address, and Birthdate. Some employees are maintenance staff, while the rest are technical staff. An employee can be either a maintenance staff or a technical staff, but not both. The company also has several projects. Attributes of PROJECT include Project_ID (identifier), Project_Name, and Start_Date. Each technical staff may be assigned to one or more projects, or may not be assigned to a project. A project must have at least one technical staff assigned, and may have any number of technical staffs assigned. A technical staffs billing rate may vary by project, and the company wishes to record the applicable billing rate (Billing_Rate) for each technical staff when assigned to a particular project. There are several buildings, each having a unique ID and address. An employee must work in at least one building. Each building must be managed by one and only one maintenance staff, and every maintenance staff must manage at least one building.