therethere' no point giving any further consideration to this link the route on which cable has just been installed is always removed from the list at this point it may not be obvious what to do next there are many potential links to choose from what do you imagine is the best strategy nowhere' the ruleremember rulefrom the listalways pick the cheapest edge actuallyyou already followed this rule when you chose which route to follow from ajothe ajo-danza edge was the cheapest here the cheapest edge is ajo-bordoso you install cable link from ajo to bordo for cost of million dollarsand build an office in bordo let' pause for moment and make general observation at given time in the cable system constructionthere are three kinds of towns towns that have offices and are linked by cable (in graph terms they're in the minimum spanning tree towns that aren' linked yet and have no officebut for which you know the cost to link them to at least one town with an office we can call these "fringetowns towns you don' know anything about at this stageajodanzaand bordo are in category colina and erizo are in category and flor is in category as shown in figure as we work our way through the algorithmtowns move from category to and from to figure partway through the minimum spanning tree algorithm building the bordo-erizo link at this pointajodanzaand bordo are connected to the cable system and have offices you already know the costs from ajo and danza to towns in category but you don' know these costs from bordo so from bordo you send out surveyors to colina and erizo they report back costs of to colina and to erizo here' the new listbordo-erizo$ million danza-colina$ million bordo-colina$ million danza-erizo$ million