1. A salary for private school teachers in Pittsburgh that would be considered efficient by economists would be:

1. When prevailing salaries have led to equality between the quantity of teachers demanded and the quantity supplied.
2. Where salaries face no pressure from the invisible hand to change over a period of time.
3. Where supply and demand intersect in this market.
4. Where self-interested teachers and private schools reach an agreement without the pressure of shortages, or the inefficiency of surpluses being part of the final outcome.

5.All of the above