Average variable costs and average total costs are calculated by dividing by ________

Short-run contractions and expansions in economic activity are called

A) recessions. B) expansions. C) deficits. D) the business cycle.

The value of a model is determined by

A) the usefulness of its predictions in the real world. B) the extent of the profit earned by applying it. C) the realism of its assumptions. D) the model's attention to real world details.