We're planning a direct mail acquisition campaign: 1 million mailers at $0.50 each, a 1% response rate, 50% of responders get approved, and each new account has an expected NPV of $120. Is this campaign worth running, and what's the minimum response rate to break even?

我们打算做一次直邮获客，寄100万封，每封成本0.5美元，回复率1%，回复的人里有50%能通过审批，每个新账户的预期NPV是120美元。你觉得这次活动值得做吗？回复率最低要到多少才能保本？