How do I find the answer for the Dec 31st entry?

Below are the entries for my assignment.

Jan 17: Sold inventory to

Otton Gomez,

$1,100

on account. Ignore cost of goods sold.

Journal Entry
Date		Accounts	Debit	Credit
Jan	17	Accounts receivable - Otton Gomez	1,100
		Sales revenue		1,100

Jun 29: Wrote off the

Otton Gomez

account as uncollectible after repeated efforts to collect from him.

Journal Entry
Date		Accounts	Debit	Credit
Jun	29	Allowance for uncollectible accounts	1,100
		Accounts receivable - Otton Gomez		1,100

Aug 6: Received

$350

from

Otton Gomez,

along with a letter stating his intention to pay within 30 days. Reinstated his account in full.

Begin by preparing the entry to reinstate the account. (Do not record the receipt of cash, this will be recorded in the next entry.)

Journal Entry
Date		Accounts	Debit	Credit
Aug	6	Accounts receivable - Otton Gomez	1,100
		Allowance for uncollectible accounts		1,100

Now prepare the entry for the receipt of

$350

from

Otton Gomez.

Journal Entry
Date		Accounts	Debit	Credit
Aug	6	Cash	350
		Accounts receivable - Otton Gomez		350

Sep 4: Received the balance due from

Otton Gomez.

Journal Entry
Date		Accounts	Debit	Credit
Sep	4	Cash	750
		Accounts receivable - Otton Gomez		750

Oct 31: Made a compound entry to write off the following accounts as uncollectible:

Brody Conrad,

$400;

Tom Marquet,

$200;

and

Susie Stein,

$700.

Journal Entry
Date		Accounts	Debit	Credit
Oct	31	Allowance for uncollectible accounts	1,300
		Accounts receivable - Brody Conrad		400
		Accounts receivable - Tom Marquet		200
		Accounts receivable - Susie Stein		700

Dec 31: Based on the aging of accounts receivable, estimated uncollectible accounts as

$3,800.

Journal Entry
Date		Accounts	Debit	Credit
Dec	31	Bad debt expense
		Allowance for uncollectible accounts

How do I find the answer for the Dec 31st entry?