Frame of Cargo Bike

FIG. 1 is a left side elevation view of a frame of cargo bike showing my new design; FIG. 2 is a right side elevation view thereof; FIG. 3 is a rear elevation view thereof; FIG. 4 is a front elevation view thereof; FIG. 5 is a top plan view thereof; FIG. 6 is a bottom plan view thereof; FIG. 7 is a top, front, and right side perspective view thereof; and, FIG. 8 is a top, front, and right side perspective view of the frame of cargo bike in its state of use thereof. The dash-dash broken lines in the drawings depict portions of the frame of cargo bike that form no part of the claimed design.