What are the possible phenotypes of chicken offspring if one parent has black feathers (FB) and one parent has white feathers (FW) ? What is the probability?

None. Chickens have feathers not fur.

Now to color. The male usually determines color so without that information it is hard to answer with any authority.

In most crosses if the male is black and the hen is white you will get some black chicks and all will have white/black

variations.

If the male is white and the hen is black you will get some all

white with others showing black and white.

If the breed is Leghorn, even if the rooster is black you will

get mostly white chicks with some throwbacks in red and buff.