Following housing market collapse, U.S. personal saving rates have

In the above figure, at any price between $8 per unit to $12 per unit, how many units will a profit-maximizing perfectly competitive firm produce?

A) None, because the producer will never choose to operate at a loss. B) Less than 20 because this will reduce marginal cost. C) Between 20 and 30, because variable costs are covered so the firm's losses will be minimized by producing rather than shutting down. D) More than 30, because variable costs are covered so that the producer can earn economic profits.

The marginal propensity to save is

a. the change in saving divided by the change in income. b. the change in income divided by the change in saving. c. saving divided by income. d. income divided by saving. e. saving divided by consumption.