2. Using the following schema: Suppliers(sid, sname, address) Parts(pid, pname, color Catalog(pid, sid, cost, rating) consider the following query: SELECT s.sname, c.cost FROM suppliers s, parts p, catalog c WHERE p.pid = c.pid AND c.sid = s.sid AND c.rating 15 AND p.name = 'screw driver' a) (10 pts) Draw a query tree using selection, projection and cross product (????). b) (10 pts) Draw a query tree that optimizes the SQL query using pushing selections