can someone help with this

Carver Hospital is considering the purchase of an attachment for its X-ray machine that will cost $3,170. The attachment will be usable for four years, after which time it will can be sold for $800. It will increase net cash inflows by $1,000 per year in the X-ray department. Training the staff to operate the new attachment will cost $500. The hospital's board of directors requires a rate of return of at least 7% on such investments. Compute the net present value of purchasing the attachment