[math-fun] Chunk & Sum (minimal rule)

Hello Allan, I have found -- thanks to a remark made to me by Frank Stevenson in a private mail -- the "minimal pieces" rule I was trying to explain. Alice always wants to check if there is a sum that is sound (according to the first rule -- increasing chunks) _and_ inferior to the sum claimed by Bob -- when considering Bob's arrangement. This is sometimes difficult to see. Best, and thanks to Frank, É.