Gold and salt were so closely linked that some west Africans even used salt as currency

Part A: what idea in the text does this sentence emphasize?

Part B: cit two other sentences from the text support, idea in part a

Part A: This sentence emphasizes the close relationship between gold and salt in West Africa.

Part B:
1. "Gold and salt were so closely linked that some west Africans even used salt as currency."
2. "Some west Africans even used salt as currency."