Our new card offers a $200 bonus if customers spend $3,000 in the first three months. We get 100,000 new accounts a year and 50% hit the threshold. Marketing wants to lower the threshold to $1,000, which should lift the hit rate to 70%. How would you set this up in Excel to see if it's worth it, and how much value does each newly qualifying customer need to bring for it to pay off?

我们新卡有个开卡奖励：三个月内刷满3000美元送200美元，每年10万新户，达标率50%。营销想把门槛降到1000美元，预计达标率升到70%。你在Excel里怎么算这件事值不值？新增的达标客户每人至少要带来多少价值才划算？