The above figure shows the market for steel ingots. If the market is competitive, then to achieve the socially optimal level of pollution, the government can
◦ institute a standard and allow firm to produce at most 50 ingots per period.
◦ institute a standard and allow firm to produce at most 10 ingots per period.
◦ institute a standard and allow firm to produce at most 25 ingots per period.
◦ institute a standard and allow firm to produce at most 100 ingots per period.