We claim the ornamental design for a bathtub, as shown and described.
FIG. 1 is a top, front, left, perspective view of an embodiment of the claimed design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a left side elevation view thereof;
FIG. 5 is a right side elevation view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof;
FIG. 8 is a cross-sectional view thereof taken across line 8-8 of FIG. 6; and,
FIG. 9 is a cross-sectional view thereof taken across line 9-9 of FIG. 6.
The ornamental design which is claimed is shown in solid lines in the drawings. The broken lines in the drawings are for illustrative purposes only and form no part of the claimed design. Broken lines formed by equal length dashes show unclaimed subject matter. Broken lines formed by unequal length dashes (i.e., dash-dot) define bounds of the claimed design. Cross-hatching provided on cut surfaces is for illustrative purposes only and forms no part of the claimed design.