Answer:
Last option 780.
Explanation:
To get the surface area for this you will need to get the area of each square that you see is in the net version. Once you do that you add them all together. Here is the math. . .
(4*25)+(4*10)+(4*25)+(10*25)+(10*25)+(4*10) = 780 total surface area.
If this looks confusing just look at the net version of the rectangular prism and you can see there is a duplicate of the different dimension triangles. These areas would be (4*25), (4*10), (10*25). There are a total of 3 different size triangles and all of them have duplicates. So we just multiply everything by 2
(4*25)+ (4*10)+(10*25) = 390 now multiply that by 2 and you get 780 again.
Hope the explanation helps :)