How many languages are spoken in Bihar

I am not from Bihar but have been working with the people of this state for a long time now. I am impressed with few who have immense knowledge of Hindi and somewhat of English. The problem in English language is that people from Bihar are not able to pronounce the accent of this language.

I just want to know as to how many languages are being spoken in this state and what is the area that is being covered by the particular language.

Hope the people on this site will make a forum response for this thread and put some knowledge here so that the people other than Bihar will come to know about this state and the languages being spoken there.