\[Q=8.5\,\rm{m^3/min}=\frac{8.5}{60}\,\rm{m^3/s}=0.14166\]
\[Q=\frac{\pi}{4}d_1^2V_1=\frac{\pi}{4}d^2_2V_2より\]
\[V_1=\frac{4Q}{\pi d_1^2}=\frac{4\times0.14166}{\pi\times0.3^2}=2.00427=2.0\,\rm{m/s}\]
\[V_2=\frac{4Q}{\pi d_2^2}=\frac{4\times0.14166}{\pi\times0.2^2}=4.50939=4.5\,\rm{m/s}\]