The cost of controlling emissions at a firm is given by
$$C(q)=4,000+100 q^{2}$$
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 $$\$ 500$$ per pound of pollutant removed. How many pounds of pollutant should the firm remove each day in order to minimize $n e t$ cost (cost minus subsidy)?