Final answer:
Duncan is declaring that he will name his eldest son, Malcolm, as the Prince of Cumberland, establishing him as the heir to the throne.
Step-by-step explanation:
In this excerpt from the play Macbeth by William Shakespeare, the subject is English literature. The question that the student asked is about understanding the meaning of a specific line spoken by Duncan. Duncan is declaring that he will name his eldest son, Malcolm, as the Prince of Cumberland, thereby establishing him as the heir to the throne. This line signifies a significant shift in the plot as it sets up Malcolm's role as the future king and creates tension for the protagonist, Macbeth.