7. The days sales outstanding (DSO) ratio of a firm identifies: a. the average length of time a firm must wait after making a credit sale before receiving cash. b. how effectively the firm uses its plant and equipment to help generate sales. c. the extent to which a firm's net operating income can safely decline. d. the profit (earnings) per dollar of sales. e. how much investors are willing to pay for the firm's stock for each dollar of reported profits.