The fund is divided into two parts. Among them, A's rate of return is fixed, such as 4%, and the rest of the investment income belongs to B. If the total * * * earns 20%, then A's share gets 4% and B's share gets 16%. If there is a loss, as long as the loss does not exceed a certain proportion (such as 80%), then the income of share A is still 4%, and share B bears all the profits and losses. If the loss exceeds a certain proportion, then both A and B shares will bear the possible losses in the next investment.