A young couple are saving money in order to make a down payment on a house 6 years from now. Suppose that they save $150 a month during the first year, $165 a month during the second year, and so on, the amount increasing by $15 a month in each successive year. What is the most expensive house that they will be able to purchase at the end of the 6-year period, if they pay 25% down? Assume that their savings earns 7% per year, compounding quarterly, Show everything you need to get to that answer-sketch, etc.