****I NEED HELP! I don't understand the calculations to these questions***

At the end of the current year, the accounts receivable account has a debit balance of $673,000 and sales for the year total $7,630,000.

1. The allowance account before adjustment has a debit balance of $9,100. Bad debt expense is estimated at 3/4 of 1% of sales.
2. The allowance account before adjustment has a debit balance of $9,100. An aging of the accounts in the customer ledger indicates estimated doubtful accounts of $29,100.
3. The allowance account before adjustment has a credit balance of $5,400. Bad debt expense is estimated at 1/2 of 1% of sales.
4. The allowance account before adjustment has a credit balance of $5,400. An aging of the accounts in the customer ledger indicates estimated doubtful accounts of $44,800.

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

Assumption	Amount
a.	$fill in the blank 1
b.	$fill in the blank 2
c.	$fill in the blank 3
d.	$fill in the blank 4