x years after 2005 (more precisely, Jan 1st 2005), the average property tax on a three bedroom home in Champaign was T(x) = 15x + 45x + 500 dollars. (a) At what rate was the property tax changing with respect to time at the start of 2007 (Jan 1st 2007)? Was the property tax increasing or decreasing at that time? (Answer the questions in part (a) with a phrase such as "Increasing at a rate of " or "Decreasing at a rate of .") (b) By how much did the property tax actually increase during 2008?