Part A:
Let:
V = Volume
r = Radius
h = Height = 20 ft
The volume of a cylinder is given by:

Answer for part A:

Part B:
From the previous equation, solve for r:
Divide both sides by 20π:

Take the square root of both sides:
![\sqrt[]{r^2}=\sqrt[]{(V)/(20\pi)}](https://img.qammunity.org/2023/formulas/mathematics/college/mfzomlo726c4qm9my54fyhmtyen9gaet7j.png)
Answer for part B:
![r=\sqrt[]{(V)/(20\pi)}](https://img.qammunity.org/2023/formulas/mathematics/college/zpukvbznjyi26w36uwq328suw4sv8n7p7o.png)
Part C:
Using the previous equation:
![r=\sqrt[]{(V)/(20\pi(3.14))}](https://img.qammunity.org/2023/formulas/mathematics/college/dbf0ldmartvx6aq4iwcybfieusrx0xsbgm.png)
Graphing the function: