Refer to the figure above .

Refer to the figure above.  If the firm above faced an emissions charge of $ t* per ton/month and the firm is producing at the socially efficient level of emissions, what is the value of the firm's total costs of emission control?

Select one:

a. t* (a+b+c+d)

b. (a+b+c+d+e)

c. (a+b+c+d)

d. (b+d+e)