Unfiltered water is pumped into a water filtration tank at a constant rate, and the filtered water is pumped out at a constant rate. At what rate, in gallons per minute, does the filtration tank fill up?

The capacity of the tank is 900 gallons.
The unfiltered water enters the tank at a rate of 30 gallons per minute, and the filtered water leaves the tank at a rate of 30 gallons every 51/3 minutes.