I need answer for the followin three questions

Table for q141-q142

140. wo firms, A and B, each currently dump tons of chemicals into the local river. The government has decided to reduce the pollution and from now on will require a pollution permit for each ton of pollution into the Firm A $100 for each ton of pollution that it eliminates before it reaches the river, and it costs Firm B $50 for each ton of pollution that it eliminates before it reaches the river.The government gives each firm 20 pollution permits. Government officials are not sure whether to allow the firms to buy or sell the pollution permits to each other. What is the total cost of reducing pollution if firms are not allowed to buy and sell pollution permits from each other? What is the total cost of reducing pollution if the firms are allowed to buy and sell permits from each other? a. $3,000; $1,500 b. $4,500; $3,500 c. $4,500; $4,000 d. $4,500; $2,500