How can i determine the value of biasing resistance R1 , R2

 

Here the R calculated for a given Iq.

https://www.electronics-tutorials.ws/amplifier/class-ab-amplifier.html

Then here a discussion of Iq in the transistors, low vs high -

http://www.diyaudio.com/forums/solid-state/58561-low-biasing-biasing-class-ab-amps.html

Regards, Dana.