smc

We can use the formula $A=P(1+rt)$ for simple interest, where $P$ is the principal (initial amount), $A$ is the total, $r$ is the interest rate per year, and $t$ is the time in years. We are solving for $P,$ so we can rearrange the equation: $$P=\frac{A}{1+rt}$$ Plug in all the necessary numbers: $$P=\frac{255.31}{1+(0.05)(2/12)}=\text{textdollar}253.21$$ So, the interest is $$P\ast (0.05)(2/12)=\text{textdollar}2.11$$ The answer is $\boxed{11}$