When you use an aging schedule approach for estimating uncollectable accounts:

a. Bad debts expense is measured indirectly, and the allowance for uncollectable accounts balance is measured indirectly.

b. Bad debts expense is measured directly, and the allowance for uncollectable accounts balance is measured indirectly.

c. Bad debts expense is measured indirectly, and the allowance for uncollectable accounts balance is measured directly.

d. Bad debts expense is measured directly, and the allowance for uncollectable accounts balance is measured directly.