Sofa

FIG. 1 is a top front perspective view of a sofa showing the claimed design; FIG. 2 is a front elevation view thereof; FIG. 3 is a right side elevation view thereof; FIG. 4 is a rear elevation view thereof; FIG. 5 is a left side elevation view thereof; FIG. 6 is a top plan view thereof; FIG. 7 is a bottom plan view thereof; FIG. 8 is a top front perspective view of another embodiment of a sofa showing the claimed design; FIG. 9 is a front elevation view thereof; FIG. 10 is a right side elevation view thereof; FIG. 11 is a rear elevation view thereof; FIG. 12 is a left side elevation view thereof; FIG. 13 is a top plan view thereof; and, FIG. 14 is a bottom plan view thereof.