A silicon sample is uniformly doped with donor type impurities with a concentration of $10^{16} / cm^3$. The electron and hole mobilities in the sample are $1200 \: cm^2/V-s$ and $400 \: cm^2/V-s$ respectively. Assume complete ionization of impurities. The charge of an electron is $1.6 \times 10^{-19} \:C$. The resistivity of the sample (in $\Omega – cm$) is ___________.