You may have missed the ''semi'' part of ''semiannually,'' and used $\displaystyle{m}={1}\usepackage{cmbright}\Huge\$ . You should be using $\displaystyle{m}={2}\usepackage{cmbright}\Huge\$ , along with $\displaystyle{P}={10},{000}\usepackage{cmbright}\Huge\$ , $\displaystyle{r}={0.05}\usepackage{cmbright}\Huge\$ , and $\displaystyle{t}={10}\usepackage{cmbright}\Huge\$ . Substitute into the formula and simplify.