Sales The sales $S$ (in thousands of units) of a new CD burner after it has been on the market $t$ years are given by $S=100\left(1-e^{k t}\right) .$ Fifteen thousand units of the new product were sold the first year.
(a) Complete the model by solving for $k$
(b) Use a graphing utility to graph the model.
(c) Use the graph in part (b) to estimate the number of units sold after 5 years.