We claim the ornamental design for a bathtub, as shown and described.
FIG. 1 is a perspective view of another cmbodimcnt of the claimed design;
FIG. 2 is a top view of the embodiment of FIG. 1;
FIG. 3 is a bottom view of the embodiment of FIG. 1;
FIG. 4 is a side view of the embodiment of FIG. 1;
FIG. 5 is another side view of the embodiment of 1;
FIG. 6 is a front view of the embodiment of FIG. 1;
FIG. 7 is a rear view of the embodiment of FIG. 1;
FIG. 8 is a cross-sectional view taken along line 8-8 in FIG. 2; and,
FIG. 9 is a cross-sectional view taken along line 9-9 in FIG. 2.
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. Broken away symbols having a jagged element show that no particular length of the portion is claimed.