I WILL GIVE PLEASE HELP Bob walks up to a tank of water that can hold 75 gallons. When it is active, a drain empties water from the tank at a constant rate. When Bob first sees the tank, it contains 15 gallons of water. 4 minutes later, the tank contains 12 gallons of water.

A. At what rate is the amount of water in the tank changing? answers: 3/4, -3, -3/4, 3
B. How many more minutes will it take for the tank to drain completely?
C. How many minutes before Bob arrived was the tank completely full?