If total profit is maximized, then marginal cost must equal marginal revenue.

When a change in the price level causes a change in the purchasing power of currency, which then changes planned real expenditures at all income levels, it is called

A) the real-balance effect. B) the open-economy effect. C) the substitution effect. D) the interest rate effect.

In the above, as the y variable increases

A) the x variable is constant. B) the x variable increases. C) the x variable decreases. D) the x variable at first increases but then decreases.