Southwest Pediatrics has the following balances on December 31, 2021, before any adjustment: Accounts Receivable = $121,000; Allowance for Uncollectible Accounts = $2,100 (debit. On December 31, 2021, Southwest estimates uncollectible accounts to be 20% of accounts receivable. Required: 1. Record the adjusting entry for uncollectible accounts on December 31, 2021. (If no entry is required for a particular transaction/event, select "No Journal Entry Required" in the first account field.)