I understand now.
In order to go down from 200 to 100 becquerels per cubic metre, you indicated—I thought really properly—the direct and indirect costs are enormous given the existing radon. If we had done the work required to reduce that risk we'd save a lot of money. Then you said that we'd probably save twice as much if we went to 100. I'm not sure that's true. To get down from 200 to 100, it wouldn't in fact be a doubling. It might be much more expensive to get to a lower level, isn't that so?