Passage: The Palace of Westminster contains over 1,100 rooms, 100 staircases and 4.8 kilometres (3 mi) of passageways, which are spread over four floors. The ground floor is occupied by offices, dining rooms and bars; the first floor (known as the principal floor) houses the main rooms of the Palace, including the debating chambers, the lobbies and the libraries. The top-two floors are used as committee rooms and offices.

Question: How many floors are in the Westminster Palace?
four