You have been engaged to design a software system for a Retail Store Management System. The Retail Store Management System is a system designed to manage stock. Typical activities include ordering, arranging and selling stock. The Retailer checks for the availability of stock items in the store. If any stock item is depleted, then the retailer places an order for those items from the supplier. After ordering new stock, the retailer pays for the stock, the supplier supplies the ordered items. The retailer then arranges the stock by product or by price, then the retailer makes a payment to the supplier. The retailer then sells the items directly to the customer. The customer buys the items they require from the retailer. The retailer prepares a bill for the items purchased by the customer, he receives a payment by credit or by cash from the customer. The supplier supplies the ordered stock to the store. The overall system is used to manage the goods in the store. Construct the following diagrams for the proposed system:

(a) Use Case Diagram.

(b) Class Diagram include any attributes, methods, multiplicity and relationships.

(c) Sequence Diagram - Managing stock.

(d) Activity Diagram - Managing stock.