What is the net present worth using an interest rate of 8.5% over 8 years from operating equipment that upfront costs 40,000, a salvage value of 4,000 at the end of the 4-year useful life assuming repeatability with the revenues and cost values given below?

	1	2	3	4	5	6	7	8
Revenue	16,000	21,000	21,000	24,000	22,000	20,000	15,500	10,500
Operating Cost	4,500	5,500	6,000	7,200	4,500	5,500	6,000	7,200