Chapter 4.4, Problem 9E

Special Rounding Instructions For this exercise set, round all regression parameters to three decimal places, but round all other answers to two decimal places unless otherwise indicated.

Cell phones The following table shows the number, in millions, of cell phone subscribers in the United States at the end of the given year.

Year	Subscribers(millions)
$2010$	$296.3$
$2011$	$316.0$
$2012$	$326.5$
$2013$	$335.6$
$2014$	$355.4$

a. Plot the data points.

b. Use exponential regression to construct an exponential model for the subscriber data.

c. Add the graph of the exponential model to the plot in part a.

d. What was the yearly percentage growth rate from the end of $2010$ through the end of $2014$ for cell phone subscribership?

e. In $2014$, an executive had a plan that could make money for the company, provided that there would be at least $380\text{million}$ cell phone subscribers by the end of $2016$. Solely on the basis of an exponential model for the data in the table, would it be reasonable for the executive to implement the plan?