To find the total surface area of the box, we have to find the area of each part.
Area of the two equal triangles.
[tex]A_{\text{triangles}}=2\frac{bh}{2}=bh[/tex]Where b = 7m and h =8m.
[tex]A_{\text{triangles}}=7m\times8m=56m^2[/tex]Now, let's find the area of each rectangle because they are different,
[tex]\begin{gathered} A_1=bh=13m\cdot7m=119m^2 \\ A_2=bh=13m\cdot8m=104m^2 \\ A_3=bh=13m\cdot10.63m=138.19m^2 \end{gathered}[/tex]Then, we add all the areas
[tex]A_{\text{total}}=56+119+104+138.19=417.19m^2[/tex]