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 $350 in Allowance for Doubtful Accounts just peior to adjustment. Analysis of Accounts Receivabie indicates uncoliectible receivables of $8,900. (b) Credit balance of $350 in Alowance for Doubtful Accounts just prior to adjustment. Uncollectble receivables are estimated at 1\% of eredit sales, which totaled $991,000 for the year