Suppose that Medical Marijuana, Inc. is currently producing at a point where its private marginal cost of production is $15.00. At this level of production, social marginal cost is $25.00. At the current production level, marginal social benefit is $15.00. Thus, the negative externality associated with Medical Marijuana Inc.'s level of production is

a. $0 because marginal private cost and marginal social cost are equal. 

b. $0 because marginal private cost and marginal social benefit are equal.

c. $25.00 per unit.

d. $15.00 per unit.

e. $10.00 per unit.