The cost of controlling emissions at a firm goes up rapidly as the amount of emissions reduced goes up. Here is a possible model, C(x, y) = 1,000 + 400x2 + 500y2, where x is the reduction in sulfur emissions, y is the reduction in lead emissions (in pounds of pollutant per day), and C is the daily cost to the firm (in dollars) of this reduction. Government clean-air subsidies amount to $200 per pound of sulfur and $200 per pound of lead removed. How many pounds of pollutant should the firm remove each day to minimize net cost (cost minus subsidy)?