A $\mathrm{G}\mathrm{e}$ specimen is doped with $\mathrm{A}\mathrm{l}$. The concentration of acceptor atoms is $~{10}^{21}\mathrm{a}\mathrm{t}\mathrm{o}\mathrm{m}\mathrm{s} {\mathrm{m}}^{-3}$. Given that the intrinsic concentration of electron-hole pair at this temperature is $~{10}^{19} {\mathrm{m}}^{-3}$, the concentration of electrons in the specimen is: