If the function g is defined by g(x)= {x/2+5 x< 7 -3x+3 x > _ 7 what is the average rate of change of g over the interval 4< _ x < _ 8

Average rate of change = [(g(7) - g(4))/(7 - 4) + (g(8) - g(7))/(8 - 7)] = [(7/2 + 5) - (4/2 + 5)]/(7 - 5) + [(-3(8) + 3) - (-3(7) + 3)]/(8 - 7) = [(8.5 - 7)/2 + (-21 - (-18))/1] = (1.5/2 + (-3)) = 0.73 - 3 = -2.25