In an underground coal mine, a fan delivers air through a cross-sectional area of \(5~\mathrm{m^2}\) with an average air velocity of \(4~\mathrm{m/s}\). What is the quantity of air circulated by the fan?
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The air quantity in a mine airway is
\[
\boxed{Q=A\times V,}
\]
where \(A\) is the cross-sectional area and \(V\) is the average air velocity.