Suppose that Michael owns a lighthouse, and Lauren owns a nearby port. Abigail's lighthouse will benefit only those ships that enter Sophia's port. Which of the following statements is not correct?
a. Abigail's lighthouse may be considered a private good.
b. Abigail can reduce the free-rider problem by charging Sophia a usage fee.
c. Abigail can exclude Sophia's port from benefit from the lighthouse by turning the power off
d. Abilgail's lighthouse would be considered a common resource