FIG. 1 is a front, top, left side perspective view of a sink showing our new design; FIG. 2 is a front view thereof; FIG. 3 is a rear side 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. Broken lines of the disclosure are for illustrative purposes only and form no part of the claimed design.