Based on the map, what was the approximate distance between Gao and Kumbi Saleh? a 200 miles b 400 miles c 600 miles d 800 miles

One drawback of voluntary trade is that it a.requires two groups to use a common language b.can make one group dependent upon another for necessary goods c.doesn't occur unless there is a shortage of goods for at least one group d.forces groups to rely on themselves to produce all the goods they need