Yes, thanks I made a mistake about the power supply voltage.
As to saturation voltage you are probbably right but in my school
they sead 0.5V and high current transistors have saturation voltage
of 5 V (if I read the datasheet correctly).
(for example BUX98A for 24A)
The saturation voltage depends on the type of transistor, the base and collector current and the temperature.
The maximum current is only 60mA so there's no need to use power transistors, an ordinary small signal transistor such as the BC548 will do.
Why are the resistor values so low?
I'd divide all the resistor and capacitors by 10 to reduce the current required. If you need a high current output, an extra booster transistor can be added.
As to saturation voltage you are probably right but in my school
they sead 0.5V and high current transistors have saturation voltage
of 5 V (if I read the datasheet correctly).
(for example BUX98A for 24A)