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 part of maintenance staff OR 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 member 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 member, and may have any number of technical staff assigned. Technical staff billing rates may vary by project, and the company wishes to record the applicable billing rate $($Billing$\_$Rate$)$ for each technical staff member when assigned to a particular project. There are a number of 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 member, and all maintenance staff must manage at least one building