$8.$ A travel$/$tour company provides a broad range of tours and travel services with discounts for their members. A member may be an individual member or a company member that allows the company$$s employees to use the services. An individual member will pay his$/$her own travel expenses, a company employee will be paid for by his$/$her company. The payment will be charged by credit card.

The travel company offers the following categories of services:

$$ Air travel $$ charters for airlines

$$ Water travel $$ cruises, barges, boats, yachts, and ferries

$$ Railroad travel $$ railroad tours and vacations

$$ Ground travel $$ tour buses, mini$-$buses and bus charter services in US and Canada

Use Enhanced ER Diagram $($EERD$)$ to design a database to track a member to use their services. The EERD must include some EERD notations such as superclass$/$subclass$,$ categories, and other constraints.

For the service entities $($such as Air travel, Water travel, Railroad travel, and Ground travel$)$ you are only expected to include key attributes $($such as the primary key$)$ to reduce the complexity of your design. For the entities which are NOT service entities $($all remaining entities$),$ you are still expected to include key attributes and non$-$key attributes.

Please clearly state any assumptions you make and your design rationale. You may use any graphical tools to draw your EERD or you can use hand$-$writing to clearly show your EERD. $(20$ points$)$