volume flow rate $=\mathrm{Av}=\mathrm{A} \sqrt{2 \mathrm{gh}}$
${=\left(2 \times 10^{-6}\right)(2 \times 10 \times 2)^{1 / 2}}$
${=4 \sqrt{10} \times 10^{-6} \mathrm{m}^{3} / \mathrm{s}}$
${\cong 12.6 \times 10^{-6} \mathrm{m}^{3} / \mathrm{s}}$

(Take acceleration due to gravity $=10\,ms ^{-2}$ )

