A retailer system manages a number of ProductIF objects for sale. Each ProductIF is either a table or a chair. The same type of product objects, such as tables, are allowed to have a different price tag due to minor cosmetic issues. The way to set the MSRP price for a product is through the setPrice method. There is also a getPrice method to return the MSRP of a product. For the purpose of information hiding and software reuse, the price attribute is preferred to be private but made sharable to all ProductiF objects. Based on the description for the existing code above, you are asked to expand the system for the customer to see MSRP plus tax based on the living state. One major requirement is not to modify the existing code. Conceptually, the new design allows the getPrice method of the customer's received ProductIF object to show the sum of MSRP and tax from the product of interest and living state. Which design pattern is a good choice for the expansion? ( 3 pts) Draw the UML class diagram for the whole system design that includes required classes, interfaces, methods, attributes and relationships. ( 9 pts)