If a Tank Holds 5000 Gallons of Water, and That $V=5000\left(1-\frac{t}{40}\right)^{2}$

Short Answer

If a tank holds 5000 gallons of water, and that water can drain from the tank in 40 minutes, then Torricelli's Law gives the volume V of water remaining in the tank after t minutes as $V=5000\left(1-\frac{t}{40}\right)^{2}$ .
Find the rate at which water is draining from the tank after 9 minutes.