Answer:
True
"GDP": Example
One city(City A) harvests 10 tomatoes produced from a local garden that are worth 3 dollars each to sell. Another city(City B) noticed city A's great farming skills, and decided to come to city A, and sell 6 of their freshly made toast for 4 dollars. The sum of city A and city B would be 54 dollars, which is regarding their economic activity and production. Therefore, the statement is true.