Draw an ER diagram for the following scenario about professors, projects, and departments:

Each professor has a pid, a name, an age, a rank, and a research specialty.

Each project has a project number $($pnum$),$ a sponsor name $($e$.$g$.,$ NSF$),$ a starting date, an

ending date, and a budget.

A project is worked on by one or more professors $($known as the project's co$-$investigators$).$

A professor may work on multiple projects.

Each department has a department number $($dno$),$ a department name, and a main office.

Each department has a professor $($known as the head$)$ who runs the department.

A professor can work in one or more departments, and for each department that he$/$she

works in$,$ a time percentage is associated with his$/$her job.

And then write SQL statements to create the corresponding relations and capture as many of

the constraints as possible. Also state the constraints that you cannot capture, if any.