Calculate the Average Rate between the points (4,f(4))\displaystyle {\left({4},{f{{\left({4}\right)}}}\right)} and (8,f(8))\displaystyle {\left({8},{f{{\left({8}\right)}}}\right)} for the funcion f(x)=10x24x\displaystyle {f{{\left({x}\right)}}}={10}{x}^{{2}}-{4}{x}.