Respuesta :

The case will have 6 surfaces

Top + Bottom  Surface = 2 x 140 x 120 = 33600 square mm
Right + Left Surface = 2 x 140 x 9 = 2520 square mm
Front and Back Surface = 2 x 120 x 9 = 2160 square mm
Total =   33600 + 2520 + 2160 = 38280 square mm