Thank you for answers Russlk and audioguru, but there must be a certain solution. This problem is one of our final examination problems. The beta values of the transistors given on the circuit should be used for the solution. For instance, for T2 the collector current Ic2 = 4A, the base current Ib2= 4/100 = 0.04 A and the emitter current Ie2= 4.04 A. By the way i've missed to indicate the GND end of the 7805, it will be directly connected to the ground. In other words the referance voltage for 7805 is 0, it's as usual.