For this case we can model the problem as a cylinder.
The volume of a cylinder is given by:

Where,
Ab: base area
h: cylinder height
Substituting values in the equation we have:

From here, we can clear the area of the base
Answer:
An equation that can be used to find the area of the circular base is:
D is the right answer because g is midpoint of ah and e is midpoint of ab and eg is parallel to bh so eg equals half bh
<h3>
Answer: 78.6</h3>
Work Shown:

Multiply across the rows to form a third column. Example: 9*90 = 810 in the first row.

The values in the third column add to 810+1440+1050 = 3300
Divide this over the total number of people which is 9+18+15 = 42
The mean is 3300/42 =78.571 approximately which rounds to 78.6