Answer:
![\large\boxed{V=226,200\ ft^3}](https://img.qammunity.org/2020/formulas/mathematics/middle-school/dv9p0gzc6xoaenne1kz9n9nnwvivgudl3d.png)
Explanation:
The formula of a volume of a prism:
![V=BH](https://img.qammunity.org/2020/formulas/mathematics/middle-school/5cp42nuplbh6iz7ybq2kknco2ra5umr2p2.png)
B - area of a base
H - height
We have the triangle in the Base. The fomula of an area of a triangle:
![A_\triangle=(bh)/(2)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/yq5cittpo1pidytq8vffdaywxan7zocf8v.png)
b - base
h - height
We have b = 58ft and h = 78ft. Substitute:
![B=((58)(78))/(2)=(29)(78)=2,262\ ft^2](https://img.qammunity.org/2020/formulas/mathematics/middle-school/pfh0pltfjfmsvbbiwp3sab8sfgd38ba2qw.png)
The volume:
B = 2,262 ft², H = 100 ft. Substitute:
![V=(2,262)(100)=226,200\ ft^3](https://img.qammunity.org/2020/formulas/mathematics/middle-school/pvzgn9rbxfonu4gf0bvglr1yhlg1zwrort.png)