Chapter 4.4, Problem 9G

To determine

The time required to reach the amount of caffeine to $40\text{ mg}$ using the graph and also describe the method when the graph and the table representing the variation in the amount (in milligrams) of caffeine in the system with the number of hours since the consumption of caffeine is as follows,

The provided table is:

Time (in hours)	Caffeine (in milligrams)
$0$	$180.0$
$1$	$144.0$
$2$	$115.2$
$3$	$92.2$
$4$	$73.7$
$5$	$59.0$
$6$	$47.2$
$7$	$37.7$