from where we get 20% interest factor for 8 years and why expalin it please

Cost Amortization of initial investment Initial cost Expected useful life Salvage value Interest cost on invested capital Annual cost =$4000(20% interest factor for 8 years ) =$40000.26061 $4000 8 years Expected cost of annual maintenance (if any) Expected annual cost due to reduction in production rate (if any) Total expected annual cost 20% Benefit Estimated tangible costs per injury of this type Estimated intangible costs per injury of this type Total costs per injury Average number of injuries per year on this machine due to this hazard Expected number of injuries of this type after guarding Expected reduction in injuries per year ( Expected benefit =$27501.1) $350 $2400 $2750 1.2 0.1 1.1 $3025 Since the total expected benefit of $3025 is more than the total expected cost of $1842, the conclusion is that it would be worthwhile to install this machine guard