The answer is 30 gallons.
Firstly, convert the hours to minutes so you know how many minutes you're working with. 2*60=120 minutes.
Then, multiply 120 with 4 to get the number of tea (in cups) that is poured. 120*4=480 cups.
Finally, divide 480 cups with 16 cups to find out the number of gallons poured. 480/16 equals 30 gallons.
Hope this helped.