When the box is disassembled, except for the upper and lower sides, it is rectangular, indicating that ants climb from the P end point of the rectangle to the Q end point.

The shortest path is the diagonal of the rectangle.

According to the box data, the rectangle is (2+4)x 2= 12cm long and 5cm wide.

Diagonal length? = 12? +5?

The shortest path is 13cm.