reserve fi,psi for Ordinal-Sequence,
  A,A1,B,C,D for Ordinal,
  X,Y for set,
  x,y for object;

theorem
  A*^B mod^ B = {}
proof
A1: A*^{} = {} by ORDINAL2:38;
A2: A*^B-^A*^B = {} by Th54;
  {}-^(A*^B div^ B)*^B = {} by Th56;
  hence thesis by A1,A2,Th68;
end;
