The questions are based on the following relational schema:

 Suppliers(sid: integer, sname: string, address: string) Parts(pid: integer, pname: string, color: string) Catalog(sid: integer, pid: integer, cost: real) 

(Please note that primary key constraints are underlined.)

The Catalog relation lists the prices charged for parts by Suppliers. Write the following queries in Relational algebra

Find the pnames of parts for which there is some supplier.

Find the snames of suppliers who supply every part.

Find the snames of suppliers who supply every red part.

Find the pname of parts supplied by Acme Widget Suppliers and no one else.

Find the sids of suppliers who supply only red parts.

Find the sids of suppliers who supply a red part and a green part.

Find the sids of suppliers who supply a red part or a green part.

For every supplier that only supplies green parts, find the snames of the supplier.

For every supplier that supplies a green part and a red part, find the snames and and cost of the most expensive part that she supplies.

Find the pids of parts supplied by at least two different suppliers.