Answer
$5.6\%$.
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 $r=0.055$ compounded quarterly ($n=4$), the amount is:
$A=P(1+\frac{0.055}{4})^{4(1)}\approx1.056P$
Thus the annual percentage yield is $5.6\%$.
