Determine the amount to be added to Nlowance for Doubtful Accounts in each of the following cases and indicate the ending balance in each case. (a) Credit balance of $420 in Alowance for Doubtful Accounts just prior to adjustment. Analysis of Accounts Receivabie incicates uncoliectible receivabies of \$p8.940. (b) Credit balance of $420 in Alowance for Doubtful Accounts just prior to adjustment. Uncollectible receivables are estimated at 3% af credit sales, which totaled 3949,000 for the year