Step-by-step explanation:
step 1. the surface area of this object is the addition of 3 rectangles and 2 triangles
step 2. the area of a rectangle is bh. the area of a triangle is (1/2)bh where b is the base and h is the height
step 3. 20*9 + 20*9 +20*6 + (1/2)6*8 + (1/2)6*8 assuming both triangles have h = 8
step 4. 180 + 180 + 120 + 24 + 24
step 5. answer: 528 cm^2
