# Rooks Attack

$$3$$ rooks are arranged on a $$27 \times 27$$ chess board so that no rook is attacking another. How many places can a $$4$$th rook be placed so that it is attacking exactly one other rook on the board?

Details and assumptions

The rook (also called castle) is a chess piece that attacks horizontally and vertically (in the same row and column).

×