Brown Company's account balances at December 31, 2020 for Accounts Receivable and the related Allowance for Doubtful Accounts are $920,000 debit and $2,100 credit, respectively. From an aging of accounts receivable, it is estimated that $39,000 of the December 31 receivables will be uncollectible. The necessary adjusting entry would include a credit to the allowance account for:_______