Allowance for Doubtful Accounts has a credit balance of $1,209 at the end of the year (before adjustment), and an analysis of customers' accounts indicates uncollectible receivables of $19,146. Which of the following entries records the proper adjustment for bad debt expense?

a.debit Allowance for Doubtful Accounts, $17,937; credit Bad Debt Expense, $17,937

b.debit Bad Debt Expense, $17,937; credit Allowance for Doubtful Accounts, $17,937

c.debit Allowance for Doubtful Accounts, $20,355; credit Bad Debt Expense, $20,355

d.debit Bad Debt Expense, $20,355; credit Allowance for Doubtful Accounts, $20,355