Answer
$ 6.168\%$
Work Step by Step
Apply the Effective Rate of Interest Theorem:
The effective rate of interest $r_{e}$ of an investment earning an annual interest rate $r$ is given by
Compounding $n$ times per year: $\displaystyle \quad r_{e}=\left(1+\frac{r}{n}\right)^{n}-1$
Continuous compounding: $\quad \quad r_{e}=e^{r}-1$
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Compounding $n=12$ times per year$, \quad r=0.06,$
$r_{e}=\displaystyle \left(1+\frac{0.06}{12}\right)^{12}-1\approx 0.06168$
$ r_{e}\approx 6.168\%$