A rule of thumb for how we think about. Well, the rule of thumb is a percentage, and it's relatively split of our cost is true fixed cost in the short term. So we try to keep that at all times at an optimal level. And the rest of our cost, we view as variable innovative, even if it's not purely variable cost and we have, as I mentioned, on input -- of all inputs, wood, chemicals and everything else and an output of all transportation and supply chain to the customer, we have a supply chain operating model, SAP-based, lots of data visibility and our goal is to minimize all of that variable cost. And every time we have to go through a period of this type of operation, we've gotten a little bit better at variabilizing more of the cost. And our people and those systems continue to learn how to manage and it's about coordination, it's about not looking at it by containerboard or cellulose fibers or Printing Papers. It's about looking the fiber converters we have, making all three of those products, taking in wood, pushing out transportation and logistics cost and warehousing costs and using chemicals and other things and optimizing that for International Paper. And that's how we look at it. So that's our rule of thumb, not a specific number, but getting back to the smallest level it can be so that we have the best possible outcome when we're not running at sort of nameplate capacity. I would add though, Mark, running like we ran in 2018 with virtually maintenance outages and nothing else, it's not actually the optimal way to run our company or to supply our customers as a service platform they need. We'll do it when the market indicates we need to do it. But something like I talked about before, 3% to 3.5% of our productive time for maintenance, planned maintenance and about the same amount for flexibility in the supply chain marginal cost optimization, the ability not to buy expensive wood when we don't have to, that's where we make the highest level of profitability and have the highest margins. And that's not the first quarter, that's more than we would like to see, but that's why we work on that variabilization of our cost structure constantly.