The following tables form part of a database held in a Relational Database Management System for a printing company that handles printing jobs for book publishers: Publisher (pubID, pubName, street, city, postcode, telNo, creditCode) Book Job (jobID, pubID, jobDate, description, jobType) PurchaseOrder (jobID, POID, poDate) PurchaseItem (jobID, POID, itemID, quantity) Item (itemID, description, onHand, price) In the above, primary keys are underlined. where: Publisher contains publisher details and publD is the key. BookJob: contains details of the printing jobs (books or part books) and jobID is the key. PurchaseOrder : A printing job requires the use of materials, such as paper and ink, which are assigned to a job via purchase orders. This table contains details of the purchase orders for each job and the key is jobID/polD. Each printing job may have several purchase orders assigned to it. Purchaseltem: Each purchase order may contain several PO items. This table contains details of the PO items and jobID/polD/itemID form the key. Item: contains details of the materials which appear in POltem, and the key is itemID. 1) How many publisher fall into each credit code category? 2) List all job type's with at least three printing jobs 3) List average price of all item 4) List all items with a price below the average price of an item. (Ctrl)