4. The VCE(sat) voltage of an npn transistor in saturation continues to decrease slowly as the base current increases. In the Ebers-Moll model, assume αF = 0.99, αR = 0.20, and Ic = 1mA. For T = 300K, determine the base current, IB, necessary to give (a) VCE (sat) = 0.30V, (b) VCE(sat) = 0.20V, and (c) VCE(sat)=0.10V.