Quality Building Supply (QBS) has proposed a project to develop a business system. The project team has gathered the following information:

The QBS stores have two kinds of customers: general public and contractors. The general public customers must supply credit card information in order to purchase any items. Their name, phone number and e-mail address are also stored for warranty/refund purposes. In addition, contractors have an account created by a QBS clerk so that they can get a specific discount. Each account thus created has a unique identifier and also stores the contractor's company name (if any), the current credit limit and the last purchase date and amount. The transactions for general public and for the contractors are accomplished by a QBS clerk who scans each item and adds them to the purchase. Items that cannot be successfully scanned are added to the purchase by hand.

If one or more items are not present on the shelf and a search reveals that the stock level is zero, they are added on an order that is created by the QBS clerk on behalf of the customer (either general public or contractor). Each order thus created has a unique identifier and stores order creation date, total amount and status (e.g. pending, closed...).

The name, price and stock level of the items stocked by QBS are recorded in the system of interest together with the item type. Items are produced by and sourced from a manufacturer, whose name and country are recorded in the system. The date of the last payment, the open balance and the date of the next shipment of items are also recorded for each manufacturer. Note that the manufacturer has no direct access to the system of interest. Also, at this stage the general public and contractors can search items online but can only purchase them in store.

The stock levels of each item are changed by the system with each purchase. However these levels need to be manually updated by a clerk in certain cases such as shipments of items from manufacturers, refunds, exchanges, etc.

Your task is (as a system analyst / designer) to prepare a report of system analysis for the above business system. Your report should consist of the following sections:

- Section 1: Identifying the use cases of the system based on the narrative above, and giving a brief description for each of the use cases.

(Please note that the narrative does not cover all the aspects of the QBS business system. You are only required to identify the use cases covered by the given information.)

From Section 2, you focus on only one use case. Although you can choose any use case identified in Section 1, we recommend that you take the use case, "Buy Items", for the following sections.

- Section 2: Developing a use case diagram.

- Section 3: Developing activity diagrams. (Please note that for the use case, "Buy Items", there are two scenarios, namely, "General public customer buys items" and "Contractor customer buys items". You should develop an activity diagram for each of the scenarios.)

- Section 4: Providing fully developed use case descriptions for the use case, (that is, a fully developed use case description for each of the scenarios).

- Section 5: Developing domain model class diagrams, (a diagram for each of the scenarios).

- Section 6: Developing system sequence diagrams, (a diagram for each of the scenarios).