If you cant move goods from one Place to another you cant trade, which means you cant bye or sell anything.
If the system ist bad, it Takes longer and costs more to Transport goods which is Bad because of the competition in the (world's)marcet(you shouldnt be too slowly and the prices very cheap)
Answer:
A convention is an agreement between 2 countries helping over a particular problem, less formal then a treaty . Also a convention is a gathering where people meet and discuss a problem or similar interests.
Kingdoms of the Iberian Peninsula
