The cost of controlling emissions at a firm is given by C(q) = 4,000 + 100q2 where q is the reduction in 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 $400 per pound of pollutant removed. How many pounds of pollutant should the firm remove each day in order to minimize net cost (cost minus subsidy)?