Hi,
My question is how do I calculate the ending balance of the allowance for uncollectible accounts using the accounts receivable aging method?

I am given A/R debit balance of $40,000, Allowance for Uncollectible Accounts has credit balance of $2,000. Net sales for the year $250,000. #% of net sales have proven uncollectible in the past. Aging of A/R accounts results in an estimate of $9,000.

My attempt at this problem is as follows-

$40,000 X 0.03 = $1,200
$1,200 debits to Uncollectible Accounts Expense
$1,200 credits to Allowance for Uncollectible Accounts
Current credit balance of $2000
Adjusting entry of $800 to bring current balance?

Confused from here, please help