Incorrect Question 20 0 / 2 pts This question has multiple answers. Select all that apply. When a good has positive externalities social marginal cost is equal to private marginal cost social marginal benefit is equal to private marginal benefit social marginal benefit is equal to private marginal benefit plus external benefit social marginal cost is equal to private marginal cost plus external cost private marginal cost is equal to social marginal cost plus external cost private marginal benefit is equal to social marginal benefit plus external benefit Incorrect Question 21 0 / 2 pts This question has multiple answers. Select all that apply. Which of the following scenario leads to the over-allocation of resources? Negative externalities O club goods Common goods positive externalities Public goods private goods