if a is side of base, then 4a = 12, a = 3

we have 4 triangles, each of base = 3, and height = 6sqrt3

area of 4 traingles = 4* 1/2 * 3 * 6sqrt(3) = 36sqrt(3)

Total area = 36sqrt(3)+4sqrt(3) = 40* sqrt(3) …ANSWER

B = base area

P = perimeter of the base

s = slant height

Surface Area = 6sqrt3 + 1/2 * 12 * 4sqrt3

= 6sqrt3 + 24sqrt3

= 30sqrt3

I think SR (the above answer) is confused with the formula, and he forgets that a regtangle is not necessarily a square.

http://www.glencoe.com/sec/math/prealg/prealg03/extra_examples/chapter11/lesson11_5.pdf

http://math.about.com/library/blmeasurement.htm

http://www.mathguide.com/lessons/SurfaceArea.html