A cube has 6 equal square faces. Area of one face = 40 × 40 = 1600. Total surface area = 6 × 1600 = 9600 square m. Total surface area means the combined area of all outside faces. A cube has 6 equal square faces, so after finding one face area, multiply by 6. The answer is in square units, so the correct choice is 9600 m².