A paper company currently produces three paper types: Letter, A4, and B4. Customers call a class's method PaperIF orderPaper(String type) to order a desired type of paper. Each paper type has a method double getUnitPrice() to return its own unit price while B4 further has a method double getBundlePrice() to return the bundle price. The paper company plans to produce more paper types in the future and hope not to modify the existing system. What design pattern you would choose to create objects of more paper types without code change? (3 pts) Draw the UML class diagram for your design with all the relationships, multiplicities, attributes and methods. (9 pts)