Calculation of electron and holes concentration

Can someone help me calculate this question and explain with steps the solution in 1 or 2 days. A semiconductor has an intrinsic carrier concentration ni = 2.0 × 1012 m^-3 at 300 K. A thin slab of this material is exposed to a light pulse of photon energy 2.1 eV and intensity 1000 W m^-2 for an interval of 1 ns. If the absorption coefficient of the semiconductor is 5.0 × 105 m^-1 at 2.1 eV, calculate the concentration of electrons and holes at 300 K immediately after the pulse and compute the product np for the following conditions: (a) If the semiconductor is intrinsic (i.e., n = p in the dark) (b) If the semiconductor is doped with a concentration of 1.0 × 1022 m^-3 of donor impurities which are fully ionised. In which of (a) and (b) is the rate of radiative recombination faster? Explain why.