Given:
a.) After 2 minutes, the tank contains 400 gallons.
b.) After 5 minutes, the tank is full.
For us to be able to determine how many gallons of water does the full tank hold, let's first determine the discharge rate of the water filling in the tank.
We get,
Since the tank is after 5 minutes of pumping water at a constant rate, we will just multiply the rate of discharge by the time it took for the tank to be full.
We get,
Therefore the volume of the tank is 1000 Gallons