3. (40 pts)

Construct an Entity-Relationship model for the following business problem. If necessary, make reasonable assumptions explicitly. For entity types, you must specify names, their attributes and at least one unique identifier. For relationship types, names (roles of participating entity types), cardinality, optionality, attributes (if any) must be specified. Your model should be based on the stated facts or explicit assumptions. In constructing your E-R diagram, follow the notations used in our class.

a) The company is organized into departments. Each department has a unique name, a unique number, and a particular employee who manages the department. We keep track of the start date when that employee began managing the department. A department may have several office spaces in our building. Each office space is represented by its room number, floor, size, an occupying department, and the maximum number of occupants.

b) A department controls a number of projects, each of which has a unique name, a unique number, and a single location.

c) We store each employees name, social security number, address, salary, sex, birth date, the direct supervisor name, and the department name he/she works for. An employee is assigned to one department but may work on several projects, which are not necessarily controlled by the same department. We keep track of the number of hours per week that an employee works on each project.