87282
Although grains such as barley have been used historically in relations of trade and barter ( Mesopotamia circa 3000 BC ) , they can be inconvenient as a medium of exchange or a standard of deferred payment due to transport and storage concerns and eventual spoilage .
 barley, Mesopotamia
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 barley, Mesopotamia