Answer: c. quantity of coal produced will be greater than the socially optimal quantity
Step-by-step explanation:
The Socially Optimal quantity is the level of production that takes into account the negative externality being produced by coal and weighs it against the marginal benefit it brings.
If coal produces the negative externality of polluting the environment here then the socially optimal quantity of coal will be less than the market equilibrium because the marker equilibrium would not have taken into account the negative externality and will lead to more coal being produced than should be.