In the sand reckoner, what does Archimedes realize about the great harbor that turns the story toward it resolution

In the passage, ‘The Sand Reckoner" Marcus’s words about needing to disembark contribute to the plot because in paragraph 2 Archimedes is trying to play mathematical games with Marcus, but Marcus is trying to get Archimedes to be serious. He is trying to get Archimedes to understand there’s a war going on and he needs to focus and stop playing games.

Packing the abacus = Facing reality, and seeing that a war is going on, and Syracuse has protected itself. Focusing and attending to the tasks at hand.

Question 72

What does Archimedes realize about the Great Harbor that brings the story to its resolution/conclusion?