Need analysis of case study in excel spreadsheet

DS3 - Lumber Production Company Considers Laser-Controlled Edger In 2 x 4 and 2 x 6 lumber production, significant amounts of wood are present in sideboards produced after the initial cutting of logs. Instead of processing the sideboards into wood chips for the paper mill, an \"edger\" is used to reclaim additional lumber, thus resulting in savings for the company. An edger is capable of reclaiming lumber by any of the following three methods: (1) removing rough edges, (2) splitting large sideboards, and (3) salvaging 2 x 4 lumber from lowquality 4 x 4 boards. Union Camp Company's engineers have discovered that a significant reduction in production costs could be achieved simply by replacing the original \"edger\" machine with a newer laser-controlled model. Old Edger: The old edger was placed in service 12 years ago and is fully depreciated. Any machine scrap value would offset the removal cost of the equipment. No market exists for this obsolete equipment. The old edger needs two operators. During the cutting operation, the operator makes edger settings based on his/her own judgment. The operator has no means of determining exactly what dimension of lumber could be recovered from a given sideboard and must guess at the proper setting to recover the highest grade of lumber. Furthermore, the old edger is not capable of salvaging good-quality 2 x 4s from poor-quality 4 x 4s. The defender can continue in service for another 5 years with proper maintenance. Current market value $0 Current book value 0 Annual maintenance cost $2,500 in year 1, increasing at a rate of 15% each year over the previous year's cost. Annual operating costs (labor and power) $65,000 New Laser-Controlled Edger: The new edger has numerous advantages over its defender. These advantages include laser beams that indicate where cuts should be made to obtain the maximum yield by the edger. The new edger requires a single operator, and labor savings will be reflected in lower operating and maintenance costs of $35,000 a year. Estimated Cost Equipment $35,700 Equipment Installation 21,500 Building 47,200 Conveyor modification 14,500 Electrical (wiring) 16,500 Sub total $135,400 Engineering 7,000 Construction management 20,000 Contingency 16,200 Total $178,600 Useful life of new edger Salvage value Building (tear down) Equipment 10 years $0 10% of the original cost Annual O&M costs $35,000 Depreciation Methods Building 39-year MACRS Equipment and 7-year installation MACRS Twenty-five percent of total mill volume passed through the edger. A 12% yield improvement is expected to be realized on this production, which will result in an improvement of total mill volume of (0.25)(0.12)=3%, or an annual savings of $57,895. (a) Should the defender be replaced now if the mill's MARR and marginal tax rate ar 15% and 40%, respectively? (b) If the defender will eventually be replaced by the current challenger, when is the optimal time to replace