Answer:
Net accounts receivable Before $18,600 and  After $18,600
Explanation:
solution
we know that here 
net accounts receivable before write-off  
Accounts Receivable = $19,600  
and Allowance for doubtful debt = $1,000
so Net accounts receivable =  $19,600 - $1,000 =  $18,600
so
Journal Entry for write off is here    
Allowance for doubtful Accounts = $500
Accounts Receivable = $500
and
Net accounts receivable after write off is    
Accounts Receivable= $19,100
and 
Allowance for doubtful debt= $500  
so Net accounts receivable = $19,100 - $500
Net accounts receivable = 8,600
so Net accounts receivable Before $18,600 and  After $18,600