$(25$ points$)$

$($a$)$ Create an ERD that correctly depicts the following requirements:

An INVOICE is written by a SALESREP. Each sales representative can write many

invoices, but each invoice is written by a single sales representative.

The INVOICE is written for a single CUSTOMER. However, each customer can have

many invoices.

An INVOICE can include many detailed lines $($LINE$),$ each of which describes one

product bought by the customer.

The product information is stored in a PRODUCT entity.

The product's vendor information is found in a VENDOR entity

The ERD must reflect business rules that you are free to define $($within reason$).$ Make

sure that your ERD reflects the conditions you require. Finally, make sure that you

include the attributes that would permit the model to be successfully implemented.

$($b$)$ Describe how your ERD might change depending on the assumptions you made in

your business rules.