<image>As shown in the figure, in a plane Cartesian coordinate system, the vertices \( B \) and \( C \) of the rectangle \( □ABCD \) are on the \( x \)-axis, while points \( A \) and \( D \) are on the graphs of the reciprocal functions \( y = -\frac{3}{x} \) (for \( x < 0 \)) and \( y = \frac{1}{x} \) (for \( x > 0 \)) respectively. Then, the area of the rectangle \( □ABCD \) is ________. 