Answer and Explanation:
The computation of the balances of the Allowance for Doubtful Accounts, Bad Debt Expense and Accounts Receivable is shown below;
For Accounts receivable  
a) Opening balance $200,000	Debit balance
b) Current year credit sales (75% of $800,000)	$600,000	Debit balance
c) (-) Current collection from accounts receivables	-$450,000	Credit balance
d) (-) Bad debt expenses	-$11,000	Credit balance
e) Closing balance of accounts receivables $339,000	Debit balance
for Allowance for Doubtful Accounts  
Allowance required as per Current year analysis (2% of (75% of $800,000)	$12,000	Credit balance
(-) Opening balance $1,000	Credit balance
$11,000	Credit balance
The journal entry is  
Bad debt expense a/c …Dr   11000  
       To Allowance for Doubtful Accounts 11000  
The Closing balance of Allowance for Doubtful Accounts	12000	Credit balance
For Bad debt expenses  
The journal entry is    
Bad debt expense a/c …Dr   11000  
       To Allowance for Doubtful Accounts 11000  
The Closing balance of Bad debt expense account	0