The roots of polynomial $ p(s) $ are:
$$ \begin{aligned}s_1 &= -529.8499\\[1 em]s_2 &= -35.075+40.0092i\\[1 em]s_3 &= -35.075-40.0092i \end{aligned} $$Polynomial $ s^3+600s^2+40000s+1500000 $ has no rational roots that can be found using Rational Root Test, so the roots were found using qubic formulas.