[60 Points] A company database contains information about Managers (identified by m_id) and Projects (identified by p_no). Managers manage projects. You will be given some situations concerning the manage relationship set. For each situation, draw an ER diagram for it using the notation taught in our class (assuming no further constrains hold).

a. Managers can manage the same project in different calendar years, and each year must be recorded.

b. Managers can manage the same project in several calendar years, and only the current year needs to be recorded.

c. Every manager must manage some project.

d. Every project is managed by exactly one manager.

e. Every manager manages exactly one project, and every project must be managed by at least one manager.

f. Suppose some projects can be jointly managed by a group of managers. You can introduce additional entity sets and relationship sets if necessary. (Here, we assume that only the latest calendar year of a project needs to be recorded.)