Pure germanium has a band gap of 0.67eV. The Fermi energy is in the middle of the

Question:

Pure germanium has a band gap of 0.67eV. The Fermi energy is in the middle of the gap.
(a) For temperatures of 250 K, 300 K, and 350 K, calculate the probability f(E) that a state at the bottom of the conduction band is occupied.
(b) For each temperature in part (a), calculate the probability that a state at the top of the valence band is empty.