We're setting the threshold for a new fraud model. Threshold A stops 800,000 dollars of fraud losses a month and falsely declines 10,000 good transactions; threshold B stops 1 million dollars but falsely declines 30,000 good transactions. The average good transaction is 100 dollars. The business asks which one to pick. How do you decide?

新欺诈模型上线前要定阈值。用阈值A每月能拦住80万美元的欺诈损失，误拒正常交易1万笔；用阈值B能拦住100万，但误拒变成3万笔。正常交易平均金额100美元。业务问你选哪个，你怎么判断？