The ornamental design for a rack, as shown and described.
FIG. 1 is a perspective view of a rack showing my new design;
FIG. 2 is a front view thereof; the opposite side being a mirror image of the shown;
FIG. 3 is a left view thereof; the opposite side being a mirror image of the shown;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a perspective view embodying the utilization of the rack in which the broken line is for illustrative purposes only and forms no part of the claimed design;
FIG. 7 is a perspective view embodying the utilization of the rack in which the broken line is for illustrative purposes only and forms no part of the claimed design;
FIG. 8 is a perspective view embodying the utilization of the rack in which the broken line is for illustrative purposes only and forms no part of the claimed design;
FIG. 9 is a perspective view embodying the utilization of the rack in which the broken line is for illustrative purposes only and forms no part of the claimed designs; and,
FIG. 10 is a perspective view embodying the utilization of the rack in which the broken line is for illustrative purposes only and forms no part of the claimed design.