surface area

The bottom triangle's base is 3 ft and its height is 2.6 ft.

Using the formula for the area of a triangle, \(\frac{bh}{2}\), we get 3.9 square feet.

 

Now for the rest of the triangles

All 3 of the other triangles have the same base and height. The base is 3 and the height is 4.

Using the formula for the area of a triangle, we get 6 square feet. There's 3 of these triangles, so we multiply 6 by 3, getting 18.

Now we add 3.9 and 18

 

So the answer is 21.9 square feet