Suppose the government wants to reduce the total pollution emitted by three local firms. Currently, each firm is creating 4 units of pollution in the area, for a total of 12 pollution units. If the government wants to reduce total pollution in the area to 6 units, it can choose between the following two methods: Available Methods to Reduce Pollution
1. The government sets pollution standards using regulation.
2. The government allocates tradable pollution permits.

Each firm faces different costs, so reducing pollution is more difficult for some firms than others. The following table shows the cost each firm faces to eliminate each unit of pollution. For each firm, assume that the cost of reducing pollution to zero (that is, eliminating all 4 units of pollution) is prohibitively expensive.

Firm First Unit of Pollution (Dollars) Cost of Eliminating the Second Unit of Pollution (Dollars) Third Unit of Pollution (Dollars)
Firm X 130 165 220
Firm Y 600 750 1,200
Firm Z 90 115 140

Meanwhile, the other employee proposes using a different strategy to achieve the government's goal of reducing pollution in the area from 12 units to 6 units. This employee suggests that the government issue two pollution permits to each firm. For each permit a firm has in its possession, it can emit 1 unit of pollution. Firms are free to trade pollution permits with one another (that is, buy and sell them) as long as both firms can agree on a price. For example, if firm X agrees to sell a permit to firm Y at an agreed-upon price, then firm Y would end up with three permits and would need to reduce its pollution by only 1 unit while firm X would end up with only one permit and would have to reduce its pollution by 3 units. Assume the negotiation and exchange of permits are costless.

Because firm Y has high pollution-reduction costs, it thinks it might be better off buying a permit from firm Z and a permit from firm X so that it doesn't have to reduce its own pollution emissions. At which of the following prices is firm Z willing to sell one of its permits to firm Y, but firm X is not?

a. $118
b. $141
c. $183
d. $650
e. $670