A customer pays in full every month and spends $20,000 a year on our card. We earn about 2% in interchange, pay 1.5% cash back, and spend about $50 a year servicing the account. Is this customer profitable for us? Walk me through it.

有个客户每个月都全额还款，一年在我们卡上刷2万美元。交换费收入大概2%，返现1.5%，每年服务成本约50美元。这个客户能给我们赚钱吗？你怎么算？