[填空题]
A cubic box of volume fi( ig vxw qs,.k-d/*m0+q/ h0cviw sh5.up/oy ,i1lr.yeid4 i,1$ \times10^{ -2}m^3$ is filled with air at atmospheric pressure at 20 $^{\circ} $ C. The box is closed and heated to 180 $^{\circ} $ C. What is the net force on each side of the box? N