The ornamental design for a rack, as shown and described.
FIG. 1 is a top, front, left perspective view of a rack showing our 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 within the shaded areas in FIGS. 1, 4, and 5 show features that form no part of the claimed design. The unshaded surfaces within the broken line features form no part of the claimed design. The uneven-length broken lines immediately adjacent to the shaded areas in FIGS. 1-5 define boundary lines of the claimed design and form no part thereof. The even-length broken lines depicting the remainder of the rack in FIGS. 1-5 show features that form no part of the claimed design.