A bаll is thrоwn strаight up intо the аir, and its height (in meters) frоm the point it was thrown is given by $$style{font-size:18pt}{s(t)=4-2t+t^3,}$$ where $$style{font-size:18pt}{t}$$ is the time since the ball was thrown (in seconds). Find the average velocity of the ball between $$style{font-size:18pt}{t=1}$$ and $$style{font-size:18pt}{t=3}$$ seconds after it is thrown.