  Recently Boyer and Mor pointed out the first conclusion of Lemma 1 in our
original paper is not correct, and therefore, the proof of Theorem 5 based on
Lemma 1 is wrong. Furthermore, they gave a direct proof for Theorem 5 and
affirmed the conclusions in our original paper. In this reply, we admit the
first conclusion of Lemma 1 is not correct, but we need to point out the second
conclusion of Lemma 1 is correct. Accordingly, all the proofs for Lemma 2,
Lemma 3, and Theorems 3--6 are only based on the the second conclusion of Lemma
1 and therefore are correct.
