Allowance for Doubtful Accounts has a credit balance of $600 at the end of the year (before adjustment), and an analysis of accounts in the customer ledger indicates doubtful accounts of 21,000. Which of the following entries journalizes the proper provision for doubtful accounts?

a.Debit Bad Debt Expense for $600 and credit Allowance for Doubtful Accounts for $600

b.Debit Allowance for Doubtful Accounts for $21,600 and credit Bad Debt Expense for $21,600

c.Debit Bad Debt Expense for $20,400 and credit Allowance for Doubtful Accounts for $20,400

d.Debit Allowance for Doubtful Accounts for $600 and credit Bad Debt Expense for $600