In an effort to be more environmentally conscious, "a homeowner may upgrade a furnace that runs on fuel oil to a natural gas unit. The investment will be $2500 installed. The cost of the natural gas will aver- age $60 per month over the year, instead of the $145 per month that the fuel oil costs. Assume energy costs increase 3% per year. If the interest rate is 9% per year, how long will it take to recover the initial investment