6-46. A large utility company is considering two mutually exclusive methods for storing its coal combustion by-products. One method is wet (slurry) storage and the second method is dry storage. The company must adopt one of those two methods for all 28 of its ash and gypsum impoundments at seven coal-fired power plants. Wet storage requires an initial investment of $2 billion, followed by annual maintenance expenses of $300 million over a 10-year period of time. Dry storage has a $2.5 billion capital investment and $150 million per year upkeep expenses over its seven-year life. If the company’s MARR is 10% per year, which method should be recommended assuming repeatability? (6.5.1)