Jackson walks up to a tank of water that can hold up to 15 gallons. When it is active, a drain empties water from the tank at a constant rate. When Jackson first see the tank, it contains 11 gallons of water. Three minutes later, the tank contains 5 gallons of water.

at what rate is the amount of water in the tank change changing? how many more minutes will it take for the tank to drain completely? how many minutes before jackson arrived was the water tank completely full?