butters is considering how many snowmobiles to purchase for his snowmobile rental business. below are his estimates of the number of snowmobile rentals per year, depending on the number of snowmobiles available. butters expects to net $10 per rental. each snowmobile costs $10,000. how many snowmobiles should butters purchase if the real interest rate is 2% and each snowmobile depreciates at the rate of 3.5% per year?