Harry Pickart, one of your clients, operates a business that rents aircraft parts to motion picture studios for use in film production. Harry purchased most of the aircraft parts at auctions held throughout the United States. At those auctions, Harry usually acquired the parts in large quantities because he speculated that he would be able to use at least some of them in his rental business. After the conclusion of a film production, the movie studio returns the aircraft parts it rented from Harry. The parts are often returned in damaged condition or with pieces missing. Harry sometimes attempts to repair a damaged part so that it can be rented again. After being subjected to wear and tear from use, however, a part deteriorates over time, which varies depending on the particular part and its treatment by the studios during rental. Harry believes that all of the aircraft parts have a useful life of less than four years and, therefore, are entitled to be classed as three-year property. Write a letter to Harry that contains your advice on whether the aircraft parts can be depreciated over three years. Also prepare a memo for the tax files. Harry's mailing address is P.O. Box 100, Sun River, OR 97707?