Sales A company introduces a new product for which the number of units sold $S$ is $S(t)=200\left(5-\frac{9}{2+t}\right)$ where $t$ is the time in months.
(a) Find the average rate of change of $S$ during the first year.
(b) During what month of the first year does $S^{\prime}(t)$ equal the average rate of change?