39. Two ants, a red one and a black one, crawl back and forth between points $A$ and $B$ on a ruler. The red ant starts from point $A$, and the black ant starts from point $B$ at the same time. The black ant's speed is 1.25 times that of the red ant. They meet for the second time at the $124 \mathrm{~cm}$ mark on the ruler, and for the third time at the $96 \mathrm{~cm}$ mark. Therefore, point $A$ is at $\qquad$ $\mathrm{cm}$ mark.
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