9. As shown in Figure $3, A$ and $B$ are two points on the graph of the function $y=\frac{k}{x}$. Points $C, D, E,$ and $F$ are on the coordinate axes, forming a square and a rectangle with points $A, B,$ and $O$. If the area of square $O C A D$ is 6, then the area of rectangle $O E B F$ is ( ).
(A) 3
(B) 6
(C) 9
(D) 12
\begin{array}{l}=\frac{1}{2}|k|=6 . \\ \text { Then } S_{\text {K } / \text { shape }}=\frac{1}{2} O E \cdot O F=\frac{1}{2}\left|x_{B} y_{B}\right| \\ =\frac{1}{2}|k|=6 . \\\end{array}