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\frac{\mathrm{d} \mathrm{V}}{\mathrm{dtt}}=4 \pi(3 \mathrm{in})^{2}(2 \, \mathrm{in} / \mathrm{min})=72 \pi \mathrm{in}^{3} / \mathrm{min} \approx 226.19 \, \mathrm{in}^{3} / \mathrm{min}