3. Consider the following schema: Suppliers (sid: integer, sname: string, address: string) Parts (pid: integer, pname: string, color: string) Catalog (sid: integer, pid: integer, cost: real) The Catalog relation lists the prices charged for parts by suppliers. Write the following queries in SQL (40 pts): a.) Find the pnames of parts for which there is some supplier. b.) For each part, find the sname of the supplier who charges the most for that part. c.) Find the sids of suppliers who supply only red parts. d.) Find the snames of suppliers who supply every part.