Answer: Approximately 191,134 ft. cubed
Explanation:
Start by finding the volume of the hemisphere, the volume formula for a hemisphere is 2/3πr^3
Substitute 39 ft. for r and you get around 124,237 ft cubed
Now for the cone, finding the height takes an extra step, but just subtract 39 from 81 (because 39 is the radius, and the radius is the distance from the center of the sphere to the edge) which will give you a height of 40.
The volume for a cone is 1/3πr^2 x h
Substitute 39 for r and 81 for h, and get a total of around 66,897 ft. cubed
Because this is a composite figure, you need to add the volume of both figures, and 124,237 + 66,897 = 191,134
Hopefully this helped!