this is BJT circuit in saturation mode, the maximum Base(IB) current it can take is 95.9uA which give the maximum saturation current of 9.59mA. which is 100 times the bse current, because Beta = 100. The value of Base current were found by changing the value of Rb and checking each times if the saturation current is 100 times the base current, if it were above or below100 times then the circuit is not in saturation mode. 42.9k OHM is the maximum right value where the equation (100 times) still hold.
