Allowance for Doubtful Accounts has a debit balance of $600 at the end of the year (before adjustment), and an analysis of accounts in the customers ledger indicates uncollectible receivables of $13,000. Which of the following entries records the proper adjusting entry for bad debt expense? O a. debit Bad Debt Expense, $12,400; credit Allowance for Doubtful Accounts, $12,400 O b. debit Bad Debt Expense, $13,600; credit Allowance for Doubtful Accounts, $13,600 O c. debit Allowance for Doubtful Accounts, $600; credit Bad Debt Expense, $600 O d. debit Bad Debt Expense, $600; credit Allowance for Doubtful Accounts, $600