In 2017 Cheyenne Corp. had net credit sales of $2770000. On January 1, 2017, Allowance for Doubtful Accounts had a credit balance of $61500. During 2017, $108000 of uncollectible accounts receivable were written off. Past experience indicates that the allowance should be 15% of the balance in receivables (percentage of receivables basis). If the accounts receivable balance at December 31 was $600000, what is the required adjustment to the Allowance for Doubtful Accounts at December 31, 2017?