A physical constant $K$ is defined as $K = \frac{\sigma \cdot T^4}{P}$, where $\sigma$ is power per area ($ext{W/m}^2$), $T$ is temperature (K), and $P$ is pressure ($ext{Pa}$). Given $ext{W} = ext{J/s} = ext{kg} \cdot ext{m}^2 / ext{s}^3$ and $ext{Pa} = ext{kg} / ( ext{m} \cdot ext{s}^2)$, what are the SI base units of $K$?