calculating Gain really urgent!!!

I have a problem wherein i need to find and plot the stability circles.I use the K-delta test to do this.

I get delta<1 and also K<1. So i cannot conjugate match for maximum gain.Somebody pls explain how i can do this problem?

The question is:

A GaAs FET has the following scattering parameters at 6 GHz (Z0 = 50 ohm)
s11 = 0.9angle -60, s12 = 0.2 angle120, s21 = 3.0 angle 60, s22 = 0.7 angle -60.
(a) Determine the stability and plot the stability circles.
(b) Design an amplifier to have the maximum gain.

part a is okay...
pls explain in detail....will be really helpful

thanks