For you need the surface area of the bottom part.
all four side are 10*2 in = 20
20*4 = 80
the top and bottom are both 10*10 = 100
100*2 = 200
total = 280 in
The surface area of the top part:
top and bottom both 5*5 = 25
25*2 = 50
all four sides are 5*8 = 40
40*4 = 160
total = 210 in
Because the top and bottom part stand on each other, you count the bottom of the top part double.
Surface area bottom part = 280
Surface area top part = 210
210+280= 490
So it probably would be 490 in.
