my question is in the below photo.

MARKET ALLOCATION, WELFARE, EXTERNA 6. What is meant by a Pareto efficient allocation of resources? Would an economy with perfect competition in all markets and no externalities generate an allocation of resources that is Pareto efficient? How does your answer change if there are some pecuniary externalities? How does it change if there are some real externalities? What is the distinction between a pecuniary externality and a real externality