Your new york based freight haul company owns a small freight train which can serve Chicago, Dallas, and Miami with one run per month. For the past three years, you have been shipping imported coal to the three cities. The return run is sometimes empty, though on occasion you have had the opportunity to tranport a shipment of wheat from Chicago or Dallas back to New York. Your company makes a profit of $$8000$ per shipment to Chicago, $$9000$ per shipment to Dallas and $$10,000$ per shipment to Miami. In the event of a return shipment from either Chicago or Fallas, your profit is increased by $$4000.$ What percentage of shipments should you assign to each city, and what are your expected monthly profits