How to compute Zl and Zs on smith chart ?

hi everybody

how can i compute Zl(impedance forward load) and Zs(impedance forward source) by given output-power,return loss,efficiency and frequency on smith chart?
actually i have a transistor(PTB 20082) which has plotted mentioned parameters and has computed Zl and Zs in 7.5watts(output power) but i need them in 2watts.

please help me!

You cannot scale the input/output impedance of a power transistor at different power levels than the given ones.

i want to design a 2watts power amplifier and i use PTB 20082 and PTB 20180 to do that. PTB 20082 converts 2w to 300mw as its input power and PTB 20180 converts that to 30mw (source can give power up to 50mw).
but in both transistors, impadances has measured in another powers. Now what can i do?

and i want to design it in one of these classes(A or B or AB or C).

Added after 1 minutes:

i have seen a picture in " RF Microelectronics by:B.Razavi page=312 " which just a little mentioned about whatever i want.

the impednces has plotted for different frequencies and just for known power P1. i want to know how to plot P1 and i think then i can plot it in P2 which i need.