If a tank holds 2000 gallons of water, which drains from the bottom of the tank in 40 minutes, then Torricelli's Law gives the volume $V$ of water remaining in the tank after $t$ minutes as $\displaystyle V = 2000 \left(1-\frac{t}{40}\right)^2 \quad 0 \leq t \leq 40$.
Find the rate at which the water is draining out of the tank after:
(a) 5 min
(b) 10 min
(c) 20 min
(d) 40 min

(a) gal/min
(b) gal/min
(c) gal/min
(d) gal/min