allowance for doubtful accounts has a credit balance of $500 at the end of the year (before adjustment), and bad debt expense is estimated at 2% of sales. if sales are $500,000, the adjusting entry for uncollectible accounts would include a.a debit to allowance for doubtful accounts of $10,500. b.a credit to allowance for doubtful accounts of $10,000. c.a credit to allowance for doubtful accounts of $9,500. d.a debit to allowance for doubtful accounts of $10,000.