= Solution
\b[<Breadth-first tree search> remains complete but is not optimal for maximizing the bonus.] Completeness depends on the finite <branching factor> and a finite successful depth, not on the objective used to compare escapes.
Use the one-row, seven-square example from part (e). The one-round escape at column $3$ leaves the fox at column $2$, so its <graph distance> to the exit, and hence the bonus, is $1$. The two-round escape at column $6$ leaves the fox at column $4$, giving bonus $2$. The earliest successful node therefore has \b[bonus $1$ when bonus $2$ is achievable]. <Breadth-first tree search> orders by rounds rather than terminal <graph distance>.
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