Question15. If an investment is growing continuously for $t$ years, its annual growth rate $r$ is given by the formula $r=\frac{1}{t} \ln \frac{P}{P_{0}}$ where $P$ is the current value and $P_{0}$ is the amount originally invested.
An investment of $\$ 13,400$ in a particular Internet company in 1992 was worth $\$ 8,040,000$ in 1998 . Find this investment's average annual growth rate during this period.