How was the residual value calculated given that the discount rate is $3\%$ ?and study period is $40$ ?years?

Initial Expenses Initial Investment Cost (one time start-up costs) Construction 1 LPSM Quantity Unit Future Expenses Operations Cost (annual costs) Heating Fuel Roof Systems Roof Insulation Roof Systems Roof Insulation 818 GALS Unit Cost Residual Value (value of facility at end of study period) 10,000 RFSF 10,000 RFSF Total Life Cycle of Alternate #1 Maintenance & Repair Cost (upkeep costs...estimate on annual basis) Replacement Cost (scheduled replacement of building system or component) 10,000 RFSF 10,000 RFSF $165,700 $165,700 $3.00 Total Cost $4.60 $6 $4.60 $6 $2,454 $46,000 $60,000 $46,000 $60,000 Years Present Value 0 40 30 50 30 50 $165,700 $56,724 $18,951 SO -$9,401 -$3,679 $228,295