Providing for doubtful accounts

At the end of the current year, the accounts receivable account has a debit balance of $$1,935,000$ and sales for the year total $$26,710,000.$

a$.$ The allowance account before adjustment has a debit balance of $$10,200.$ Bad debt expense is estimated at $\frac{1}{2}$ of $1\%$ of sales.

b$.$ The allowance account before adjustment has a debit balance of $$10,200.$ An aging of the accounts in the customer ledger indicates estimated doubtful accounts of $$175,000.$

c$.$ The allowance account before adjustment has a credit balance of $$25,760.$ Bad debt expense is estimated at $\frac{3}{4}$ of $1\%$ of sales.

d$.$ The allowance account before adjustment has a credit balance of $$25,760.$ An aging of the accounts in the customer ledger indicates estimated doubtful accounts of $$170,420.$

Determine the amount of the adjusting entry to provide for doubtful accounts under each of the assumptions $($a through d$)$ listed above.

a$.$ $

b$.$ $

c$.$ $

d$.$ $