A small company heats its building using a gas furnace. It expects to spend $8,800 on natural gas this first year. The cost of the natural gas is expected to increase by 10% per year every subsequent year. There is also the maintenance cost on the gas furnace which is expected to be $851.20 in the first year and to increase by 12% per year every subsequent year. The planning horizon is 13 years and the company uses an annual interest rate of 15% for economic analysis of its investments. (a) The projected annual cost of natural gas in year 13 is $ (Round to nearest dollar) (b) The projected annual maintenance cost of the furnace in year 13 is $ (Round to nearest dollar) (c) The total present worth of operating and maintaining the furnace over the 13 years is $ (Round to nearest dollar)