Chapter 4.4, Problem 4E

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.

Postal Rates The table below shows the cost $s$, in cents, of a domestic first-class postage stamp in the United States $t\text{years}$ after $1900$.

$t=time,inyearssince1900$	$s=costofstamp$
$19$	2
$32$	$3$
$58$	$4$
$71$	$8$
$78$	$15$
$85$	$22$
$95$	$32$
$102$	$37$
$109$	$44$
$116$	$47$

a. Use exponential regression to model $s$ as an exponential function of $t$.

b. What cost does your model give for a $1988$ stamp? Report your answer to the nearest cent. (The actual cost was $25\text{cents}$.)

c. Plot the data and the exponential model.