We claim the ornamental design for a sofa, as shown and described.
FIG. 1 is a front perspective view of a sofa according to an embodiment of the invention. The view from the adjacent front corner being a mirror image thereof.
FIG. 2 is a front elevational view of a sofa according to an embodiment of the invention.
FIG. 3 is a top view of a sofa according to an embodiment of the invention.
FIG. 4 is a back elevational view of a sofa according to an embodiment of the invention; and,
FIG. 5 is a side elevational view of a sofa according to an embodiment of the invention. The view from the opposite side being a mirror image thereof.