Daniel Barenboim sells and erects shell houses, that is, frame structures that are completely finished on the outside but are unfinished on the inside except for flooring, partition studding, and ceiling joists. Shell houses are sold chiefly to customers who are handy with. tools and who have time to do the interior wiring, plumbing, wall completion and finishing, and other work necessary to make the shell houses livable dwellings. Barenboim buys shell houses from a manufacturer in unassembled packages consisting of all lumber, roofing, doors, windows, and similar materials necessary to complete a shell house. Upon commencing operations in a new area, Barenboim buys or leases land as a site for its local warehouse, field office, and display houses. Sample display houses are erected at a total cost of $30,000 to $44,000 including the cost of the unassembled packages. The chief element of cost of the display houses is the unassembled packages, inasmuch as erection is a short, low-cost operation. Old sample models are torn down or altered into new models every 3 to 7 years. Sample display houses have little salvage value because dismantling and moving costs amount to nearly as much as the cost of an unassembled package. Would it be preferable to amortize the cost of display houses on the basis of (1) the passage of time or (2) the number of shell houses sold? Explain