Design a Library Management System

Requirements

• The library has books, each potentially with multiple physical copies.
• A member can search the catalog, check out an available copy, and return it.
• Checkouts have a due date; overdue returns incur a fine.
• Different member types (regular, student) have different checkout limits and loan durations.

Key classes to identify before you look at the reference

The tricky part of this problem: "Book" and "physical copy of a book" are two different concepts that most first attempts conflate into one class — what breaks if you don't separate them? Also consider: different member types having different rules (checkout limits, loan duration) is exactly the shape of a problem Strategy or a simple type hierarchy can solve — which fits better here, and why?