Logic Riddles

Question: Why are pianos hard to open?

Question: In the books of a famous writter, How many letter in Those Books?

Question: A man in a wheelchair is being pushed across a hallway by his wife. When they get to the end of the hallway the man says: stop pushing me. His wife asks why, and the man gets up and starts walking. How did the man get up and start walking if he was in a wheelchair?

Question: What can be stolen legally, it is not illegal to steal it?

Question: What are the next 3 words in the sequence: j,f,m,a,m,j,j,a,s_,_, and _?