Answer
$n=15625$.
Work Step by Step
If the margin of error is $\pm0.8\%$, then our equation is: $\pm\frac{1}{\sqrt n}\cdot 100\%=\pm0.8\%=\pm0.008\\\frac{1}{\sqrt n}=0.008\\125=\sqrt{n}\\n=15625$.
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