If an investment is growing continuously for $t$ years, its anmal growth rate $r$ is given by the following formula, where $P$ is the current value and $P_{0}$ is the amount originally invested.
$$r=\frac{1}{t} \ln \frac{P}{P_{0}}$$
Suppose you graph the function $f(x)=\ln x$ on a coordinate grid with a unit distance of 1 centimeter on the $x$ - and $y$ -axes. How far out must you go on the $x$ -axis so that $f(x)=12 ?$ Give your result to the nearest mile.