Refer to the accompanying table, where Q represents the quantity produced, internal cost and social cost are given for various quantities, and P represents the price consumers are willing to pay for various quantities, to answer the following questions. Q Internal Cost Social Cost P 100 $40 $60 200 $80 $50 $70 300 $70 $60 $80 400 $60 $70 $90 500 $50 $80 $100 600 $90 $40 $110 $30 The external cost is equal to per unit. O $60 O $50 O $20 O $70 O $30