reserve a, b, n for Nat,
  r for Real,
  f for FinSequence of REAL;
reserve p for Prime;

theorem Th20:
  for A being set holds Product EmptyBag A = 1
proof
  let A be set;
  set b = EmptyBag A;
  set cS = canFS(support b);
  b*cS = <*>COMPLEX;
  hence thesis by Def5,RVSUM_1:94;
end;
