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) Which tables can be joined? C. customers customer_id first_name last_name phone email street staffs staff_id first_name last_name email phone active store_id manager_id state zip_code 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 order_id "item_id product_id quantity list price discount