Answer:
Usually pounds (lb) .About an an average of 20 to 25 pounds (lbs)
Step-by-step explanation:
Since Marvin uses Customary units, and considering the Watermelon.
Pounds, He could estimate based on average of 20 to 25 pounds.
He could choose another customary units, but it wouldn't be practical and unusual to say a watermelon of 160 quarters, also it would leave all the listeners without parameters.
So, definitely pounds.
