4. There are two firms that emit pollutant SO2. Currently each emits 150 tons of SO2 per month. Assume the pollution abatement technology of the two firms can be represented by MC functions: MCA = 30 + 2QA, MCB = 50 + 4QB (MC is in terms of dollars and Q in terms of tons of SO2 abated). Suppose the government issues to each firm 100 pollution permits which allow the firm to emit 100 tons of SO2, and the permits can be traded by these two firms. a) Which firm will want to sell permits and which will buy? b) Eventually how many permits will be traded? c) What will be the price for the last permit? d) Eventually how many tons of SO2 will firm A emit? How many tons of SO2 will firm B emit? e) How much is the net gain firm A obtains from permit trade? What about firm B? 5. An industry that is characterized by a decreasing cost struch