The mean value thrm basically says that if you take the slope of the line from the point (a, f(a)) and (b, f(b)), then somewhere between a and b, you would find a value, call it c, such that f'(c) = slope of the line from the point (a, f(a)) and (b, f(b)). So, basically, calculate the slope (96.2F - 59.6F)/ (6 hrs ) [the difference between 2pm and 8am), so the rise in temp at some point would be 6.1F/1hr