Based on Walker (1974). The Smalltown Fire Department currently has seven conventional ladder companies and seven alarm boxes. The two closest ladder companies to each alarm box are listed in the file P06_63.xlsx. The town council wants to maximize the number of conventional ladder companies that can be replaced with “tower” ladder companies. Unfortunately, political considerations dictate that a conventional company can be replaced only if, after replacement, at least one of the two closest companies to each alarm box is still a conventional company. Determine how to maximize the number of conventional companies that can be replaced by tower companies.