Backpack

FIG. 1 is a front, left and top perspective view of a backpack, showing my new design. FIG. 2 is a rear, right and bottom perspective view thereof. FIG. 3 is a front elevation view thereof. FIG. 4 is a rear elevation view thereof. FIG. 5 is a left side elevation view thereof. FIG. 6 is a right side elevation view thereof. FIG. 7 is a top plan view thereof. FIG. 8 is a bottom plan view thereof. FIG. 9 is an enlarged view of detail 9 in FIG. 1 . FIG. 10 is an enlarged view of detail 10 in FIG. 1 . FIG. 11 is an enlarged view of detail 11 in FIG. 1 ; and, FIG. 12 is an enlarged view of detail 12 in FIG. 2 . The dashed broken lines depict portions of the backpack that form no part of the claimed design. The dot-dash broken lines in FIGS. 1 - 2 and 9 - 12 depict the boundaries of the enlarged views and form no part of the claimed design. The dash dot dot dash broken lines depict stitching and form no part of the claim.