Answer:

Explanation:
we know that
The surface area of the square pyramid is equal to the area of the square base plus the area of its four lateral triangular faces
so
![SA=b^(2)+4[(1)/(2)bh]](https://img.qammunity.org/2020/formulas/mathematics/middle-school/okl6laks97netobs528c7r2f4z6ks1812c.png)
where
b is the length side of the square base
h is the height of the triangular face
Remember that
Each lateral triangular face is a triangle 45°-90°-45°
so

we have

so

substitute in the formula
![SA=6^(2)+4[(1)/(2)(6)(3)]=72\ ft^(2)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/mbjooq5dadqnzuu7nsbrlcclpuz7i5r42w.png)