RELATIONAL ALGEBRA HELP THANKS

3. Consider the following relational schema, where the primary keys are underlined, Suppliers(sid, sname, address) Parts(pid, pname, color) Catalog(sid, pid, price) Write the following queries in relational algebra. a) Find the sids of suppliers who supply red parts. b) Find the sids of suppliers who do not supply any red parts. c) Find the sids of suppliers who only supply red parts. d) Find the sids of suppliers who supply ALL the red parts