19 months ago the price of a barrel of WTI crude oil was about $100. On Monday, October10, 2016, it was $50.55 per barrel for a November 2016 contract.Could you explain by using boththe demand and supply curves why the WTI oil price has decreased so precipitously? There arefour major countries involved in the oil supply and demand market: Iran, US, Saudi Arabia, and China. Note: WTI stands for Western Texas Intermediate for light and low sulfur crude oil.