Answer:
27%
Explanation:
The computation of the net profit margin is shown below;
As we know that 
net profit margin = Net profit ÷ sales
where 
net profit is 
<u>Particulars                                                                 Amount </u>
Sales (200 customers × $12 × 350 days) $840,000 
Less: cost of goods sold (200 customers × $4.50 × 350 days) -$315,000
Gross profit $525,000
Less:
Selling and admin expense -$98,510
Depreciation expense - $20,000
Bank loan interest -$76,265
Net income before tax $330,225
Less tax at 32% -$105,672
Net income after tax $224,553
Now the net profit margin is 
= $224,553 ÷ $840,000
= 27%