A firm submits their financial records to a bank. Upon examination, the bank discovers that this firm has $$500$ in cash, $$2,050$ in accounts receivables, $$1,000$ in inventory, $$5,450$ in plant and equipment and that their assets totaled $$9,000.$ In addition, this bank discovered that the firm had $$2,000$ in current liabilities, $$2,500$ in long$-$term debt, and $$4,500$ in net worth. Finally, this bank discovered that this firm had $$20,000$ in net sales and $$2,000$ in net income. What is this firm's net working capital?