In 1873, the iron mine run by Merritt, a German who immigrated to the United States, ran into trouble due to a shortage of funds due to the U.S. economic crisis. This iron ore company had already attracted the interest of American oil tycoon Rockefeller and was determined to annex him. So Rockefeller bribed local pastor Lloyd to use hard-to-get tactics to lure Merritt. Lloyd approached Merritt and offered to help him financially to get out of trouble. Lloyd said: "There is a rich man who is my friend. For my sake, he is willing to lend you a huge sum of money at an interest rate that is 2% lower than a bank loan." Merritt was overjoyed after hearing this. A note was made: "Now Merritt has borrowed a loan of 420,000 yuan from Kaul, with an interest of 3%. This note is hereby issued as proof." Then he considered it carefully, and signed the note after thinking that there were no loopholes. Unexpectedly, six months later, Lloyd came to Merritt and said, "My friend who lent you the money is Rockefeller. He wrote a letter saying that he would immediately claim back the 420,000 yuan loan." Merritt was unable to repay the loan and was taken to court as a defendant. The plaintiff's lawyer spoke in court in accordance with American law: "The Kaul loan is a loan that the lender can claim back at any time, so its interest is lower than ordinary Loan interest. The IOU clearly stated that Merritt was borrowing a Kaul loan. Under U.S. law, borrowers must either pay back immediately or declare bankruptcy. Merritt, who had no idea what the "Call Loan" was, was initially trapped by Lloyd and fell into Rockefeller's hard-to-get plot. He had no choice but to reluctantly sell the mine to Rockefeller for 520,000 yuan.