Determine the amount to be added to Allowance for Doubtful accounts in each of the following cases. (a) Balance of $500 in the allowance account just prior to adjustment. Analysis of accounts receivable indicates doubtful accounts of $9,500. (b) Balance of $950 in the allowance account just prior to adjustment. Uncollectibles are estimated at 2.5% of sales, which totaled $1,000,000 for the year.