The ornamental design for a sofa, as shown and described.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
FIG. 1 is a front view of the sofa;
FIG. 2 is a left side perspective view of the sofa;
FIG. 3 is a rear view of the sofa;
FIG. 4 is a left side view of the sofa, the right side being a mirror image thereof;
FIG. 5 is a top view of the sofa; and,
FIG. 6 is a front view of the sofa showing two sections of the sofa spaced apart.