The average high temperature each month in a calendar year for a city in South Carolina is represented by the function (x) = x + 13.3.x + 42, where x is the month. Find the average rate of change from September to December. A) -1.7/month bicycle helmets B) -11.6/month swim goggles C) -7.7/month tutus D) 5.8/month ski masks E) 6.4/month tuxedos