To calculate the volume of the upside-down pyramid (which is essentially a rectangular pyramid), we can use the formula for the volume \( V \) of a pyramid:
\[ V = \frac{1}{3} \times \text{Base Area} \times \text{Height} \]
In this case:
- The base of the pyramid is a rectangle with dimensions 50 feet by 20 feet.
- The area of the base (Base Area) is:
\[ \text{Base Area} = 50 , \text{feet} \times 20 , \text{feet} = 1000 , \text{square feet} \]
- The height of the pyramid is the depth of the lagoon, which is 25 feet.
Now, we can substitute these values into the volume formula:
\[ V = \frac{1}{3} \times 1000 , \text{ft}^2 \times 25 , \text{ft} \]
Calculating this gives:
\[ V = \frac{1}{3} \times 1000 \times 25 = \frac{25000}{3} \approx 8333.33 , \text{ft}^3 \]
Therefore, the lagoon holds approximately 8,333.33 cubic feet.
So the correct response is:
8,333.33 ft.³ (or 8,333.33 feet cubed).