at year-end, chief company has a balance of $20,000 in accounts receivable of which $2,000 is more than 30 days overdue. chief has a credit balance of $200 in the allowance for doubtful accounts before any year-end adjustments. using the aging of accounts receivable method, chief estimates that 1.5% of current accounts and 10% of accounts over thirty days are uncollectible. what is the amount of bad debt expense?