reserve k,n for Nat,
  x,y,z,y1,y2 for object,X,Y for set,
  f,g for Function;
reserve p,q,r,s,t for XFinSequence;
reserve D for set;
reserve i for Nat;
reserve m for Nat,
        D for non empty set;
reserve l for Nat;
reserve M for Nat;
reserve m,n for Nat;
reserve x1,x2,x3,x4 for object;
reserve e,u for object;

theorem
  for D being set, p being XFinSequence of D holds rng p = rng XFS2FS p
proof
  let D be set, p be XFinSequence of D;
  thus rng p = rng FS2XFS XFS2FS p
    .= rng XFS2FS p by Th15;
end;
