Life / The rate on Polish Stamps! Please help. [3]

I am desperately trying to find information for a school project. I would like to know the current rate for first class stamps in Poland. If there is none, what is a very typical amount for a stamp? Also, I have seen a lot of Polish stamps. There is always "Polska" on it, does it ever get abbreviated to PL or anything else?

Any help is greatly appreciated!