please show work by hand not excel

9-4. A manufacturer moves pallets of materials with a forklift truck. He has consistently used the same make and model of forklift over the past several years. The purchase price has been relatively constant at $8,000 each. Records of operation and maintenance indicate these average expenses per year as a function of age of the vehicle: Year $4,000 $4,500 $3,000 $3.500 $3,000 Operating Expense The salvage (market) values of the forklift are also reasonably well known as a function of age Year $2.500 $1.250 5,000 $6,000 $4,000 15% per year (9.6 Find the best time to replace a forklift truck when the MARR