John and Sally Claussen are contemplating the purchase of a hardware store from John Duggan. The Claussens anticipate that the store will generate cash flows of $72,000 per year for 20 years. At the end of 20 years, they intend to sell the store for an estimated $420,000. The Claussens will finance the investment with a variable rate mortgage. Interest rates will increase twice during the 20-year life of the mortgage. Accordingly, the Claussens