consider a mail order database in which employees take orders for parts from customers. the data requirements are summarized as follows: the mail order company has employees, each identified by a unique employee number, first and last name, and zip code. each customer of the company is identified by a unique customer number, first and last name, and zip code. each part sold by the company is identified by a unique part number, a part name, price, and quantity in stock. each order placed by a customer is taken by an employee and is given a unique order number. each order contains specified quantities of one or more parts. each order has a date of receipt as well as an expected ship date. the actual ship date is also recorded. draw an er using class notation with all cardinality constraints.