Asoftware package created by navarro & associates can be used for analyzing and designing three-sided guyed towers and three- and four-sided self-supporting towers. a single-user license will cost $4,000 per year. a site license has a one-time cost of $15,000. a structural engineering consulting company is trying to decide between two alternatives: first, to buy one single-user license now and one each year for the next 4 years (which will provide 5 years of service); or second, to buy a site license now. determine which strategy should be adopted at an interest rate of 12% per year for a 5-year planning period, using the present worth method of evaluation.