the wall street journal presented data suggesting that united airlines was not covering its costs on flights from san francisco to washington d.c,. the article quoted analysts saying that united should discontinue this service. the costs per flight included the costs of fuel, pilots, attendants, food, etc. used on the flights. they also included shared costs associated with running the hubs at the two airports, such as ticket agents, building charges, baggage handlers, gate charges, etc. suppose that the revenue collected on the typical united flight from san francisco to washington does not cover the costs. does this fact imply that united should discontinue these flights? what could we learn from this case of study?