Cubic stack would mean all the sides are the same length.
The length of the side is given as 3 yards.
Volume = 3^3 = 3 x 3 x 3 = 27
Volume = 27 cubic yards.
The answer is 972 m^2
This is because there are 4 triangles (18*18/2) + one square (18*18) = 972
