A small company heats its building and spends ​$7 comma 800 per year on natural gas for this purpose. Cost increases of natural gas are expected to be 10​% per year starting one year from now​ (i.e., the first cash flow is ​$8 comma 580 at EOY​ one). Their maintenance on the gas furnace is ​$345 per​ year, and this expense is expected to increase by 12​% per year starting one year from now​ (i.e., the first cash flow for this expense is ​$386.40 at the EOY​ one). If the planning horizon is 15 ​years, what is the total annual equivalent expense for operating and maintaining the​ furnace? The interest rate is 15​% per year.