GLMH Shipping is a start-up company that plans to offer same-day shipping services between 20 major cities in the U.S. In order to provide this service, GLMH needs to build hubs at airports in several of these cities. GLMH wants to select hub locations in a way that ensures each of the 20 cities is within 500 miles of at least one of the hub locations. The file Airports.xlsx contains data describing the estimated cost of establishing a hub in each city as well as a matrix summarizing the distances in miles between each of the cities.

a. Create a spreadsheet model to determine where hubs should be located in order to achieve GLMH's objectives in the most cost effective manner.

b. In what cities should GLMH create hubs and what is the total cost of this plan?