[
  "Subtract twice the thickness from each outer dimension: 80-4=76, 50-4=46, 40-4=36.",
  "Multiply the inner dimensions to get volume: 76 x 46 x 36.",
  "Calculate step by step: 76 x 46 = 3,496; then 3,496 x 36 = 125,856 cubic cm."
]