The demand and supply of petrol and coal are affected by various factors including weather. During winter, more coal is consumed, while during summer, people drive more to cooler countries. The exchange value of oil, which is typically traded in US dollars, also plays a crucial role in determining the price and demand for oil. A fall in the value of the dollar can increase demand and prices, while an increase in the value of the dollar has the opposite effect. The report concludes that understanding these factors is essential to ensure adequate supply meets customer demand.