Lets say we are given a simple CE amplifier(with voltage divider on base and Rc, Re resistances)

If we are given Ic=3mA , Vcc=20V , β=100, Rth=10kΩ, Vce=10V, how can we calculate the values for R1 and R2?

Also, how can we calculate them if we are not givven the equivalent Rth value?

Thank you in advance.