If Potter's luncheon averages 4 cups of tea per minute, and Elantra lasts 2 hours, we can calculate the total number of cups of tea needed by multiplying the cups per minute by the number of minutes in 2 hours.
4 cups/minute * 60 minutes/hour * 2 hours = 480 cups of tea
Now, since there are 16 cups in one gallon, we can convert the cups to gallons:
480 cups / 16 cups/gallon = 30 gallons
So, the caterer should bring 30 gallons of tea for the event.