Sofa

FIG. 1 is a top, front and left side perspective view of a sofa showing my new design; FIG. 2 is a bottom, rear and right side perspective view thereof; FIG. 3 is a front elevational view thereof; FIG. 4 is a rear elevational view thereof; FIG. 5 is a left side view thereof; FIG. 6 is a right side view thereof; FIG. 7 is a top plan view thereof; FIG. 8 is a bottom plan view thereof; and, FIG. 9 is an enlarged view of portion 9 in FIG. 1 . The evenly dashed broken lines in the drawings illustrate portions of the sofa which form no part of the claimed design. The unevenly dashed broken lines illustrate the boundary of the enlarged view and form no part of the claimed design.