Determine the amount to be added to Allowance for Doubtful Accounts in each of the following cases and indicate the ending balance in each case.

a$.$ Credit balance of $$400$ in Allowance for Doubtful Accounts just prior to adjustment. Using the aging method, the balance of Allowance for Doubtful Accounts is estimated as $$8,300.$

Amount added

$

Ending balance

$

b$.$ Credit balance of $$400$ in Allowance for Doubtful Accounts just prior to adjustment. Bad debt expense is estimated at $1\%$ of credit sales, which totaled $$1,176,000$ for the year.

Amount added

Ending balance

$ $$

$