10^16 cm-3 phosphorous atoms are introduced in a silicon giving rise to a donor level ED. Assuming Eg = 1.1eV, NC = 2.8 x 10^19(T/300)1.5 cm-3, NV = 1.0 x1019(T/300)1.5 cm-3, EC-ED = 0.045 eV, ni (for Si) = 1.5 x 10^10 cm-3 and KBT= 0.026 eV at 300 K. Find the value of (a) Electron concentration at 300 K. (b) Electron concentration at 20 K. (c) Position of Fermi Level at 300 K. (d) Position of Fermi Level at 20 K.