a. a. Answer the following questions according to below database schema figure. State the names of all tables State the primary keys of the tables b. State the foreign keys in the tables (if any) C. Which tables can be joined? customers * customer_id first_name last_name phone email street city state zip_code staffs staff_id first_name last_name email phone active store_id manager_id orders order_id customer_id order_status order_date required_date shipped_date store_id staff_id stores store_id store_name phone email street city ++ + state zip_code order_items et order_id *item_id product_id quantity list_price discount