Answer:
D
Step-by-step explanation:
Since we start with 10,080 gallons after 0 minutes pass, we see the next point. Luckily, we are given an exact point of a number between 10,080 and 8640. The difference of those two numbers is 1440, and divide that by 2 to get 720. So we drain 720 per hour. HOWEVER, it says "minutes", so we divide 720 by 60 (hour -> minutes) to get 12.
*The reason I divided by 2 was to get the number of gallons after 1 hour passes*
