Draw E-R (Entity-Relationship) diagrams only for each problem.

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 any 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. Attributes of CHEMICAL include Compound No and Cost. The organization wishes to record Volume Used-- that is, the amount of a given chemical used by a particular chemists working on a specified project. A chemist must be assigned to at least one project and one chemical on each project to which he or she is assigned. A given chemical need not be assigned to any project, and a given project need not be assigned to either a chemist or a chemical. (HINT: Ternary relationship)

C.) A college course may have one or more scheduled sections or may not have a scheduled section. Attributes of COURSE include Course ID, Course Name, and Units. Attributes of SECTION include Section Number and Semester ID. Semester ID is composed of two parts: Semester and Year. Section Number is an integer (such as 1 or 2) that distinguishes one section from another for the same course but does not uniquely identify a section. (HINT: strong/weak entities)