Start: Operating profit before WC changes = 85,000.
Less: Increase in Trade receivables (6,000) = 79,000.
Add: Increase in Trade payables (4,000) = 83,000.
Cash generated from operations = 83,000.
Less: Tax paid (opening provision) 8,000 = 75,000.
Cash and bank overdraft are part of cash and cash equivalents, not WC. Net cash flow from operating activities after tax = Rs.75,000.