Help with Questions to Macbeth : Act IV, Scene I

Act IV, Scene I

1. What is the message of each of the three apparitions?
2. What is the significance of the form each apparition takes?
3. What is the answer to Macbeth’s question: “shall Banquo’s issue ever / Reign in this kingdom?”
4. What is the historical significance of the apparition’s answer to Macbeth’s question about “Banquo’s issue”?