The surface area of a quadrangular pyramid is exactly the area of those four triangles … because the square at the bottom is connected with the cube below, not the surface.

Firstly, the height of triangle is obtained by pythagorean theorem, that is, the general pythagorean is the height of four pyramids and the base length of four pyramids.

In this case, we can know that the height under the root sign is 1. + 1? = root number 2

Then base divided by height divided by two = triangle area = root number two.

Multiply by four to get the surface area of a quadrangular prism.

The surface areas of the lower cubes add up, because the top surface is connected with the triangular pyramid, so it is not a surface.

So it's square area ×5.

2×2×5=20

So choose a, 20+4 times the root number 2.