Problem 3: Saturation by a harmonically modulated signal. [20 points] A time varying signal is applied to a collection of non-degenerate absorbing twolevel atoms. This signal is tuned exactly to the transition frequency {03, and is amplitude- modulated at a low-frequency com: W12[t] = W21[t] = W3 + Wh cos[mmt]. The modulation depth is small, so that Wh