III. Database design (25 points)

Design a database for a mobile phone company to provide to its dealers to assist them in maintaining customer records and dealer inventory and to assist sales staff in ordering phones.

Each phone is identified by a phone identification number (PIN). Each individual phone is a particular model of a particular brand offered by the company (e.g., the P40pro a model of the phone brand Huawei of Huawei Company). Each model can be offered weith a variety of options, but an individual phone may have only some (or none) of the available options. The database needs to store information about models, brands, and options, as well as information about individual dealers, customers, and phones.

Your design should include an E-R diagram, a set of relational schemas, and a list of constraints, including primary-key and foreign-key constraints.