A tank full of water is leaking at a constant rate for 30 minutes.

The equation y=-9x + 500 gives the amount of water in the tank, where y is the number of liters and xis
the number of minutes since the tank began to leak.

Which statement is true?

A. There were 9 liters in the tank when the leak started, and it is
decreasing by 500 liters per minute.

B. There were 500 liters in the tank when the leak started, and it is
decreasing by 9 liters per minute.

C. There were 9 liters in the tank when the leak started, and it is
increasing by 500 liters per minute.

D. There were 500 liters in the tank after 30 minutes, and it is decreasing by 9 liters per minute.