Here's a simple per-account annual profit model: $15,000 annual spend, 2% interchange, 1.5% cash back, $2,000 average revolving balance, 22% APR, 5% cost of funds, 5% loss rate, and $50 operating cost per account. If we flex each assumption up and down by 20%, which one moves profit the most? How would you present this to your boss in Excel?

我给你一个单户年利润的简单模型：年消费1.5万美元，交换费2%，返现1.5%，平均循环余额2000美元，APR 22%，资金成本5%，损失率5%，运营成本每户50美元。如果每个假设都上下浮动20%，哪个对利润影响最大？你会怎么在Excel里呈现给老板？