How many square centimetres is the surface area of a rectangle made of 3 squares with 8 cm edges?

How many square centimetres is the surface area of a rectangle made of 3 squares with 8 cm edges?

Each joint covers two surfaces, and three are connected together with two joints, that is, the original surface area is less than four surfaces
8 * 8 * 6 * 3-8 * 8 * 4 = 896 square centimeters