At the end of the current year, the accounts receivable account has a debit balance of $999,000 and sales for the year total $11,330,000. The allowance account before adjustment has a debit balance of $13,500. Bad debt expense is estimated at 1/4 of 1% of sales. The allowance account before adjustment has a debit balance of $13,500. An aging of the accounts in the customer ledger indicates estimated doubtful accounts of $43,200. The allowance account before adjustment has a credit balance of $6,400. Bad debt expense is estimated at 1/2 of 1% of sales. The allowance account before adjustment has a credit balance of $6,400. An aging of the accounts in the customer ledger indicates estimated doubtful accounts of $53,100. Determine the amount of the adjusting entry to provide for doubtful accounts under each of the assumptions (a through d) listed above.