You can't really calculate that. You don't know that. It lingered on a cruise ship for 17 days with no people on it. We don't know how much longer it can linger and what conditions make that possible. It could be, that after all of our "mitigation," it spreads again when we open up again. It could end up being, that most people will have to get this in the end to achieve "herd immunity," and the only real cure in the end is a vaccine. It could end up that the shut down is causing more harm than good. We won't know until we have opened the economy up again for several weeks or months.