Option D is correct. In case of Perfect Price discrimination under monopoly, the firm will set the price equal to marginal willingness of each consumer and will be in equilibrium when price is equal to his marginal cost. It means the equilibrium price is equal to $10. At that price he would sell 5 unit. As Fred Willingess to pay is less than his marginal cost hence he will not sell to fred.
econ 101: chap 31 F Econ 101: chap Econ 101: chap 35 con 101: chap 36...