Sofa

FIG. 1 is a perspective view of a sofa showing my new design; FIG. 2 is a front view thereof; FIG. 3 is a rear view thereof; FIG. 4 is a left side view thereof; FIG. 5 is a right side view thereof; FIG. 6 is a top view thereof; and, FIG. 7 is a bottom view thereof. The even length broken lines represent portions of the sofa which form no part of the claimed design. The pair of parallel vertically-oriented, dash-dot style broken lines extending from the front to the rear of the sofa design represents an unclaimed boundary of the design, and the appearance of any portion of the sofa between these parallel, vertically-oriented, dot-dash-dot style broken lines forms no part of the claimed design.