reserve x,y,z, X,Y,Z for set,
  n for Element of NAT;
reserve A for set,
  D for non empty set,
  a,b,c,l,r for Element of D,
  o,o9 for BinOp of D,
  f,g,h for Function of A,D;
reserve G for non empty multMagma;

theorem Th28:
  for m being Multiset of X holds dom m = X & rng m c= NAT
proof
  let m be Multiset of X;
  m is Function of X,NAT by Th27;
  hence thesis by FUNCT_2:def 1,RELAT_1:def 19;
end;
