When the box is designed as a strip, its length should be 6× 12=72 cm, its width should be 6 cm and its height should be 13 cm, so the paper cover required for the box is 72×6× 13=56 16 cm.

When the box is rectangular, the length is 6×6=36 cm, the width is 2×6= 12 cm, and the height is still 13 cm, so the paper cover required for the box is 36×12×13 = 5616.

When the box is designed as another rectangle with a length of 4×6=24 cm, a width of 3×6= 18 cm and a height of 13 cm, the required paper cover is 24×18×13 = 5616.