Please show all steps and formulas used in excel. Please do not copy and paste previous answers to this problem as they are all incorrect. Thanks!

7. In a typical year, J. B. Hunt Transport Services Inc. (JBHT) purchases hundreds of new over- the-road tractors. A certain type of tractor has a retail price of $100,000. End-of-year book values, salvage values, and annual operations and maintenance (O&M) costs over its useful life are provided in the following table. O&M Costs EOY Book Value Salvage Value $80,000 $15,000 $53,000 $48,000 $39,000 $21,000 $28,000 $27,000 $28,800 $34,000 $17,280 $18,000 $5,760 $42,000 $14,000 $6,000 $49,000 Determine the economic life of this type of tractor given that the MARR is 15% and the marginal tax rate is 40%