# Quasi Fermi Levels

I can't figure out what equation to use.

A si sample with 10^15/cm^3 donors is uniformly optically excited at room temperature such that 10^19 EHPs (Electron Hole Pairs) are generated per second. Find the separation of the quasi Fermi level and the change of conductivity upon shinig the light. Electron and hole lifetimes are both 10μs. =12. {Hint: to find Fn-Fp , use the relation relating (np) and nd (ni, Fn, Fp). μn=1300[cm^2/ V-s].

I know that Fn and Fp are the quasi fermi electron and hole levels. And I know the common quasi formulas are
n=(ni)(e^-(ei-Fn)/KT)
p=(ni)(e^-(-Fp-Ei)/KT)

How do I use these equations to find the separation of the quasi fermi level?

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