In order to calculate the total surface area of this figure, let's consider the following views:
From above: 2 rectangles, one with dimensions 8 and 6 and one with dimensions 12 and 6.
From below: 1 rectangle with dimensions 20 and 6.
From the right: 2 rectangles, both with dimensions 6 and 4.
From the left: 1 rectangle with dimensions 6 and 8.
From the front and back: 2 composite figures, made by 2 rectangles each, one with dimensions 8 and 4 and one with dimensions 20 and 4.
So the total surface area is:
[tex]\begin{gathered} S=(8\cdot6+12\cdot6)+(20\cdot6)+2\cdot(6\cdot4)+(6\cdot8)+2\cdot(8\cdot4+20\cdot4) \\ S=120+120+48+48+224 \\ S=560\text{ cm}^2 \end{gathered}[/tex]Therefore the surface area of the figure is equal to 560 cm².