Hard math please can anyone help?

Question

Approximate the volume of the regular triangular pyramid if the height is approximately 11.5. the base edges of length 12 and a slant height of 12.

The answer is either
239
276
717
828

Answer 1

The volume of a pyramid is the area of the base x height / 3

For the base triangle, you can verify that the altitude
= 6*sqrt(3)
area of base = 6*sqrt(3) * 12 / 2 = 36*sqrt(3)

If the height = 11.5
volume = 36*sqrt(3) * 11.5 / 3
= 239