If the price difference is reduced, you can make a profit. Now the price difference between the two contracts PTA in May and PTA in September is =-3 12. When the price difference becomes -300, that is, the absolute value of the price difference decreases by 12 points, and you gain 12 points ~ ~

Usually, buying the latest May contract and selling the September contract is to predict that the gap between the two months will narrow, which means that the increase in May will be greater than that in September. If the prediction is correct, you will earn ~ ~