Answer
$8.789\times 10^{-9}s^{-1}$
Work Step by Step
We find the half life and we convert the units
$k=\frac{0.693}{2.5y}\times \frac{1h}{3600s}\times \frac{1d}{24h}\times \frac{1y}{365d}=8.789\times 10^{-9}s^{-1}$
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