The room temperature electrical conductivity of silicon carbide is 10-4 (Omega-m) - 1. An extrinsic n-type material is desired having a room temperature conductivity of 20 (\Omega -m) - 1. Bismuth is used as electron-receptor impurity. Determine its concentration in atom percentage to yield these electrical characteristics. Assume the electron and hole mobilities are 0.09 and 0.032 m2 /V-s; and the atomic weight and density of silicon carbide are 40.96 amu and 3160 kg/m3, respectively.