Figure 1 displays a network consisting of 5 cities (indexed by A through E), 6 major roads connecting neighboring cities, and the traveling time (in hours) across each road. We seek to locate facilities in cities A-E to cover the emergency medical service demand arising from these cities, which arehA =8,hB =8,hC =1,hD =1,andhE =9,respectively. Eachfacilityis able to cover any medical emergency within Dc hours of driving