(a) The required conductivity of a silicon material must be \(\sigma=1.5(\Omega-\mathrm{cm})^{-1}\). If \(\mu_{n}=1000 \mathrm{~cm}^{2} / \mathrm{V}-\mathrm{s}\) and \(\mu_{p}=375 \mathrm{~cm}^{2} / \mathrm{V}-\mathrm{s}\), what concentration of donor atoms must be added?

(b) The required conductivity of a silicon material must be \(\sigma=0.8(\Omega-\mathrm{cm})^{-1}\). If \(\mu_{n}=1200 \mathrm{~cm}^{2} / \mathrm{V}-\mathrm{s}\) and \(\mu_{p}=400 \mathrm{~cm}^{2} / \mathrm{V}-\mathrm{s}\), what concentration of acceptor atoms must be added?