A cyclist completes a $60$-meter sprint in $18$ seconds. The table below shows the total distance traveled as a function of time at $3$-second intervals.
Time (seconds) | Distance (meters)
:-:|:-:|:-:|
$0$ | $0$
$3$ | $3$
$6$ | $7$
$9$ | $21$
$12$ | $36$
$15$ | $50$
$18$ | $60$
**During which $3$-second interval is the cyclist's average speed greatest?**
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