$\frac{b}{m}=\frac{g}{25}$
$\omega=\sqrt{\frac{\mathrm{k}}{\mathrm{m}}-\frac{\mathrm{b}^{2}}{4 \mathrm{m}^{2}}}=\sqrt{\frac{300}{3}-\frac{1}{4} \times\left(\frac{10}{25}\right)^{2}}$
$=\sqrt{100-\frac{1}{25}}=10\left(1-\frac{1}{2} \times \frac{1}{2500}\right)$
$=9.998 \mathrm{rad} / \mathrm{s}$