$${c = \frac{1}{\sqrt{\varepsilon_0 \mu_0}} = \frac{1}{\sqrt{\frac{1}{4 \pi \cdot 9 \cdot 10^9} 4 \pi \cdot 10^{-7}}} \approx 3 \cdot 10^8\, \mathrm{\frac{m}{s}}}$$