1. (10 points) As shown in the figure, a square pond with a side length of 12 meters is surrounded by grass. There are wooden stakes at points $A$, $B$, $C$, and $D$ on the pond's edge, and $A B=B C=C D=3$ meters. Now, a 4-meter-long rope is used to tie a sheep to one of these wooden stakes. To maximize the area where the sheep can graze on the grass, the rope should be tied to the stake at $\qquad$.