2) Please develop a domain model using the UML class diagram technique for the domain described in the case below. (30 points) WSP, a wireless service provider that operates in 27 metropolitan areas in 15 states, is growing rapidly and gaining new customers because of its high-quality network and a cooperative agreement with a large national provider. WSP needs a database application that will be used for customer care and billing. It has two types of customers, individuals (for whom the company needs to maintain social security number, name, street address, city, zip, state, and e-mail address) and business customers (the same information excluding the SSN with an additional attribute contact person). Each individual customer has one of the company's calling plans, each of which defines the number of minutes, number of text messages, charges for minutes and messages exceeding the contract amounts, amount of data included in the plan, and the monthly charge for the plan. Some plans include long-distance and roaming charges, some don't. Business customers are businesses that have agreed to provide WSP's services to a certain number of their employees. They receive a percentage discount specified in a contract; the percentage is renegotiated annually, and it is essential that historical information about the contracts is maintained in the database (including start date, end date, discount percentage, and the minimum number of employees required for the contract). The employees of a business customer are treated in the same way as regular individual customers, except that their bills will be aggregated and sent to the business customer with the discount deducted. The system has to maintain information about all billing items, which at this point include calls, text messages, and data exceeding the contract total. For all billing items, the system needs to maintain the recipient's phone number, and for calls, the start and end times of the call. There is no charge for incoming text messages but information is required about incoming calls. For customer support purposes, WSP needs to maintain information (date and time, support employee, problem description, proposed solution) about support calls that it receives from its individual customers.