\[66\ 150 = 60\ 000 \cdot \left( 1 + \frac{p}{100} \right)^{2}\]
\[\frac{66150}{60000} = \left( 1 + \frac{p}{100} \right)^{2}\]
\[\frac{441}{400} = \left( 1 + \frac{p}{100} \right)^{2}\]
\[1 + \frac{p}{100} = \frac{21}{20}\]
\[\frac{p}{100} = \frac{21}{20} - 1 = \frac{1}{20}\]
\[p = \frac{100}{20} = 5\]
\[Ответ:5\%.\]