Given the following relational database schema

    hotel( hno, name, city )
    room ( hno, rno, type, price)
    guest( gno, name, street, city, state, zip )
    book ( gno, hno, rno, fromDate, toDate)

Express the following queries in Relational Algrbra expression.


1. List the hotel name, and its room information if there is
   matching room at hotel Gosvenor Hotel. By matching room,
   I mean the room type is the same and prince is the same.

2. List hotels which has rooms less than $20 and greater than
   $1,000 at the city where Mr. John Doe is living.

3. List hotels which has at least two rooms with price > $1,000.

4. List all hotels which is located at the same city as Gosvenor
   Hotel, and having rooms less than $40.

5. List detail guest information with the number of bookings,
   including the guests who have no booking yet.

6. List detail guest information for those who have exactly two
   books in one of hotels.

7. List guests who have booked rooms at least in two different
   hotels.

8. List guests who booked two or times in the same hotels.

9. List guests who booked only in the same hotels located in
   the same cities as they live.

10. List guests who book only in hotels outside of his living
    cities.

11. List guests who booked in each of all hotels in the database.

12. List the guests who have booked in each of all hotels in
    his/her city.

13. (Worst hotel) List the hotels which have no coming back guests.

14. List guests who booked at one room which is at least the
    same or more expensive than the most expensive room that
    John Do has booked.

15. List guests who have booked only rooms which is more expensive
    than the most expensive rooms that John Do has booked.

16. List each hotel, and its total gross earning in the year of 2003.

17. For each hotels and it room type, list the maximun, minimun and
    average price, and number of rooms.