1. **State the problem:** Calculate the volume of a cylindrical hay bale with diameter 5 ft and height 4 ft using the formula for the volume of a cylinder. 2. **Formula:** The volume $V$ of a cylinder is given by $$V = Bh = \pi r^2 h$$ where $r$ is the radius and $h$ is the height. 3. **Identify values:** Diameter $= 5$ ft, so radius $r = \frac{5}{2} = 2.5$ ft, and height $h = 4$ ft. 4. **Calculate volume:** $$V = \pi (2.5)^2 \times 4$$ $$= \pi \times 6.25 \times 4$$ $$= \pi \times 25$$ 5. **Final volume:** $$V = 25\pi \approx 78.54 \text{ cubic feet}$$ This means the hay bale has a volume of approximately 78.54 cubic feet.