The chapter asserts, by analogy, that in freeze-out (no acceptors present) the electron density varies as n∝e−Ed/2kBT, the same halving as the intrinsic case, but does not derive it. Derive this result from the same reasoning used earlier in the chapter for ni. Then use it to find the factor by which n changes between 50K and 60K, deep in freeze-out, for phosphorus-doped silicon (Ed=45meV).