[
  "Outer dimensions add 6 cm (3 cm per side) to each inner dimension: 126 x 86 x 56.",
  "Compute outer volume: 126 x 86 = 10,836; 10,836 x 56 = 606,816 cubic cm.",
  "Inner volume is 120 x 80 x 50 = 480,000. Foam = 606,816 - 480,000 = 126,816 cubic cm."
]