Investor a sells A-3000 points and the settlement price is 3030 points. A made up the difference of 30 points (A lost 30 points in short selling that day).

Investors buy at B-3060 points, and the settlement price is 3030 points, and B makes up the difference of 30 points (B loses 30 points on the same day).

Because the futures margin trading system needs to be settled on the same day, it needs to be replenished on the same day! Calculate the profit and loss of all parties on that day!