What is the rate of water pouring out of a drain after 28 minutes.

The floor drain is opened on a 24000-gallon pool. If the pool empties in 220 minutes then, according to Torricelli's Law, the volume of water $t$ minutes after opening the drain is given by $V=24000(1-\frac{t}{220})^2$. At what rate is the water pouring out of the drain 28 minutes after opening the drain.

So do I solve for V and then divide that by 28 minutes? I'm confused.

You should differentiate $V$ with respect to $t$, and then plug in the given value for $t$ ($t=28$) in the new equation.