a$.$ A company has a number of employees. The attributes of EMPLOYEE include Employee ID $($identifier$),$ Name, Address, and Birthdate. The company also has several projects. Attributes of PROJECT include Project ID $($identifier$),$ Project Name, and Start Date. Each employee may be assigned to one or more projects or may not be assigned to a project. A project must have at least one employee assigned and may have a number of employees assigned. An employee's billing rate may vary by project, and the company wishes to record the applicable billing rate $($Billing Rate$)$ for each employee when assigned to a particular project.b$.$ A laboratory has several chemists who work on one or more projects. Chemists also may use certain chemicals on each project. Attributes of CHEMIST include Employee ID $($identifier$),$ Name, and Phone No$.$ Attributes of PROJECT include Project ID $($identifier$)$ and Start Date.