The base area is just the area of a square = 0.9^2 = 0.81 ft^2
Nickolas.....we have four triangles comprising the sides
Their height = 4ft and their base = 0.9 ft
So....their total area = 4 (1/2) base * height = 4(1/2) (0.9) (4) = 2 (0.9)(4) = 8 (0.9) = 7.2 ft^2
So the toal suface area = [ 0.81 + 7.2] ft^2 = 8.01 ft^2