CUSTOMER (Cust#, Cname, City)

Question

ORDER (Order#, Odate, Cust#, Ord_Amt)
ORDER_ITEM (Order#, Item#, Qty)
ITEM (Item#, Unit_price)
SHIPMENT (Order#, Warehouse#, Ship_date)
WAREHOUSE (Warehouse#, City)

Given the database model above, propose a solution for the below business requirement:
Business requirement: Assume this database belongs to an e-commerce application and the company has several warehouses in different cities. The company wants to optimize its item shipment time. You can propose a series of SQL queries. Explain your answer in details.