The barrel has 60 gallons and water leaks at a rate of 1 gallon per 10 minutes.
The graph goes by 100 minutes so 100x1 = 10 gallon leaked per 100 minutes.
The graph would be a line segment as you would start at 60 gallons and end at 0 gallons, you cannot have negative gallons.
The graph is a negative line as you are losing gallons.
