Answer
$8.3\%$.
Work Step by Step
In $A(t)=P(1+\frac{r}{n})^{nt}$ for compound interest $P,r,n,t$ respectively stand for the principal, interest rate per year, the number of times the interest is compounded per year and the number of years. $A(t)$ is the amount after $t=1$ year. So if we invest $P$ at an interest rate of $r=0.08$ compounded monthly ($n=12$), the amount is:
$A=P(1+\frac{0.08}{12})^{12(1)}\approx1.083P$
Thus the annual percentage yield is $8.3\%$.
