Answer:
The correct words for the blank spaces are (in that order): low; high; opportunity; reservation.
Explanation:
For buyers and sellers to benefit from a transaction, the price of the goods or services offered must be at equilibrium. It implies the price is low enough for consumers to consider purchasing the product and high enough for producers to offer it earning a profit.
Besides, producers should consider their opportunity costs which are the costs of adding one more unit for production. On the other side of the road, consumers consumer their reservation price which is the maximum amount of money they could pay for a good or service based on the value they give to the product.