-15a - 9c -6 should be right :)
Hi there! The answer is C.
The area of the square in the middle is the following:
Hence, the area of the square is 25 cm^2.
The area of one triangle is the following:
Hence, the total area of the four triangles is 4 × 20 = 80 cm^2.
Therefore, the total area of the pyramid is 80 + 25 = 105 cm^2. The answer is C.