Hello. Please look at the attached figure first, which is cut image from transistor section of HyperPhysics. In this circuit, I only need to know base current or base voltage, IB. In order to know this VB must be known but it is already given as 0.6 V. How this value is obtained? I don't think this is given parameter for each transistor and it seems enough external parameters to fully describe this circuit is already specified. Could you please figure out What I've missed in circuit analysis?