Cost benefit analysis is a way of helping you organize your tolts. But the pretence that we to know everything to a precise decimal point is what undermines, in the end, these attempts to construct the net benefit of a project. A valuet risk is a flawed measure. It's an attempt to possess the riskiness investment portfolio. And its its practitioners certainly recognize that it's imperfect. We would you e know, what's the alternative? That's our best measure. How do you react to that? John?