A 2,000 square foot house in New Jersey costs $1,725 each winter to heat with its existing oil-burning furnace. For an investment of $5,000, a natural gas furnace can be installed, and the winer heating bill is estimated to be $1,000. If the homeowner's MARR is 6% per year, what is the discounted payback period of this proposed investment?
(a) 7 years
(b) 8 years
(c) 9 years
(d) 10 years