Allowance for Bad Debts has a credit balance of $9,000 at the end of the year (before adjustment), and an analysis using percent of sales indicates an estimated $49,000 bad debts. Which of the following entries would correctly record the adjustment to the allowance for bad debts?

a. debit Bad Debts Expense, $58,000; credit Allowance for Bad Debts, $58,000

b. debit Bad Debts Expense, $49,000; credit Allowance for Bad Debts, $49,000

c. debit Allowance for Bad Debts, $49,000; credit Bad Debt Expense, $49,000

d. debit Allowance for Bad Debts, $58,000; credit Bad Debt Expense, $58,000

The answer is B."debit Bad Debts Expense, $49,000; credit Allowance for Bad Debts, $49,000"

I need someone to explain why this is the correct answer, and a formula on how to do it.

Thank you