4) Library Management System ER Diagram:
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                                    +-------------+
                                    |    Member   |
                                    +-------------+
                                    | member_id (PK)|
                                    | name        |
                                    | email       |
                                    | address     |
                                    +-------------+
                                            |
                                            |
                                  +---------+---------+
                                  |                   |
                          +-------+-------+   +-------+-------+
                          |     Borrows   |   |    Book       |
                          |               |   +---------------+
                          +---------------+   | book_id (PK)  |
                          | borrow_id (PK)|   | title         |
                          | member_id (FK)|   | author        |
                          | book_id (FK)  |   | available     |
                          | borrow_date   |   +---------------+
                          | return_date   |
                          +---------------+