Net Profit Ratio = Net Profit after tax / Revenue from Operations x 100
Net Profit = Gross Profit - Salaries and Rent - Interest on Debentures + Gain on Sales of Furniture
= Rs 80, 000 - Rs 30, 000 - Rs 5,000 + Rs 2,000
Net Profit = RS 47,000
Net profit Ratio = Rs 47,000 / Rs 4,00,000 x 100 = 11.75 %