recall that the average rate of change is simply the slope.
[tex]\bf \begin{array}{|cc|ll} \cline{1-2} years&price\\ \cline{1-2} 0&0.90\\ 5&1.20\\ \cline{1-2} \end{array}~\hfill (\stackrel{x_1}{0}~,~\stackrel{y_1}{0.90})\qquad (\stackrel{x_2}{5}~,~\stackrel{y_2}{1.20}) \\\\\\ slope = m\implies \cfrac{\stackrel{rise}{ y_2- y_1}}{\stackrel{run}{ x_2- x_1}}\implies \cfrac{1.20-0.90}{5-0}\implies \cfrac{0.30}{5}\implies \stackrel{\textit{6 cents per year}}{0.06}[/tex]
