9. Person A and Person B start from points $A$ and $B$ respectively at the same time and walk towards each other. When A reaches the midpoint of $A B$, the two are 5 kilometers apart; when B reaches the midpoint of $A B$, the two are $\frac{45}{8}$ kilometers apart. The distance between $A$ and $B$ is $\qquad$ kilometers.
\begin{tabular}{c}
9 \\
\hline 90
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