A 50 gallon fish tank is leaking at a constant rate. When Ben first sees the tank, it contains 42 gallons of water. 7 minutes later, the tank contains 28 gallons of water. 1. At what rate is the amount of water in the tank changing? Use signed number, & include the unit of measurement in your answer. 2. How many more minutes will it take for the tank to drain completely? Explain or show your reasoning. 3. How many minutes before Ben arrived was the water tank completely full? Explain or show your reasoning.