We claim the ornamental design for a bell, substantially as shown and described.
FIG. 1 is a perspective view of a bell in accordance with the present design.
FIG. 2 is a front view thereof.
FIG. 3 is a back 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 broken lines immediately adjacent the claimed subject matter represent the bounds of the claimed design. All other broken lines depict environmental subject matter only and form no part of the claimed design.