reserve n,m,k for Nat,
  x,y for set,
  r for Real;
reserve C,D for non empty finite set,
  a for FinSequence of bool D;

theorem Th18:
  for F be PartFunc of D,REAL, A be RearrangmentGen of C st F is
  total & card C = card D holds Sum (Rland(F,A),C) = Sum (F,D)
proof
  let F be PartFunc of D,REAL, B be RearrangmentGen of C;
  assume F is total & card C = card D;
  then FinS(Rland(F,B),C) = FinS(F,D) by Th17;
  hence Sum(Rland(F,B),C) = Sum FinS(F,D) by RFUNCT_3:def 14
    .= Sum (F,D) by RFUNCT_3:def 14;
end;
