a. What amount do customers owe Grainger at each of the year-ends 2013 through 2015?

b. What percentage of its total accounts receivable does Grainger deem uncollectible?

Interpreting Accounts Receivable and Related Footnote Disclosure Following is the current asset section from the W.W. Grainger Inc. balance sheet. As of December 31 ($ 000s) 2015 2014 2013 $ 290,136 226,644 430,644 Cash and cash equivalents. . . . Accounts receivable (less allowances for doubtful accounts of $22,288, $22,121 and $20,096, 1,209,641 1,172,924 1,101,656 1,414,177 1,356,396 1,305,520 85,670102,669 115,331 0 61,387 75,819 15,315 $3,048,642 $2,967,549 $3,044,285 Prepaid expenses and other assets.. . . . . .. Deferred income taxes. . 49,018 47,529 Grainger reports the following footnote relating to its receivables. reports the following footmote relating to its receivables The following table shows the activity in the allowance Allowance for Doubtful Accounts for doubtful accounts. For Years Ended December 31 ($ 000s) 2015 2014 2013 . $22,121 $20,096 $19,449 8,855 Write-off of uncollectible accounts, net of recoveries. . (10,495) 9,628) (7,942) 266) $22,288 $22,121 $20,096 Balance at beginning of period Business acquisitions, foreign currency and other. 481 (1,292)