[
  "The largest cube side is limited by the shortest dimension: min(20, 16, 12) = 12 cm.",
  "Cuboid volume = 20 x 16 x 12 = 3,840. Cube volume = 12^3 = 1,728 cubic cm.",
  "Remaining = 3,840 - 1,728 = 2,112 cubic cm."
]