Using the data presented in Figure $12\mathrm{.}16$ on the right, determine the number of free electrons per atom for intrinsic germanium and silicon at room temperature $(298$ K $).$ The densities for Ge and Si are $5\mathrm{.}32\frac{g}{c}{m}^3$ and $2\mathrm{.}33\frac{g}{c}{m}^3,$ respectively. The answer for Si is around $2$x$10^-12$ and for Ge is $9$x$10^-10.$ Not sure how these answers were found