Answer: THE LAST OPTION
Step-by-step explanation:
The formula for calcualte the surface area of a cone is the shown below:
[tex]SA=rs\pi+r^{2}\pi[/tex]
Where s is the slant height and r is the radius.
You can see in the figure that s=21ft and the r=12ft.
Then when you substitute values, you obtain that the result is:
[tex]SA=(12ft)(21ft)\pi+(12ft)^{2}\pi=396\pi[/tex]ft²
