What do free entry and exit refer to?
a. the ability of businesses to hire and fire staff as needed for rising and falling levels of production
b. the ability of businesses to begin or end production and sales according to profitability
c. the entry of mergers and exit of small producers common in perfectly competitive markets
d. the repetitive process of the rise and fall of demand in the marketplace?

by using  production possibilities graph.  opportunity costs are key expenses in financial matters and are utilized as a part of registering money saving advantage investigation of a venture. such expenses, be that as it may, are not recorded in the record books but rather are perceived in basic leadership by processing the money costs and their subsequent benefit or misfortune.

the boundarys like convergent divergent and transform it causes subduction