The area of the shape is 230 cm.
a)
Check the picture below.
b)
volume wise, we know the smaller pyramid is 1/8 th of the whole pyramid, so the volume of the whole pyramid must be 8/8 th.
Now, if we take off 1/8 th of the volume of whole pyramid, what the whole pyramid is left with is 7/8 th of its total volume, and that 7/8 th is the truncated part, because the 1/8 we chopped off from it, is the volume of the tiny pyramid atop.
Now, what's the ratio of the tiny pyramid to the truncated bottom?

Rate = 2 seats/11 minutes = 2/11 seats/min
Therefore the time required for s seats is

That is,
m = (11s)/2 min
When s = 16, obtain

When s = 19, obtain

Answers:

When s = 16, m = 88 min
When s = 19, m = 104.5 min