During testing of single cylinder two-stroke petrol engine, following data were obtained-brake torque \(=640 \mathrm{Nm}\); cylinder diameter \(=21 \mathrm{~cm}\), speed \(=250 \mathrm{rpm} ;\) stroke \(=28 \mathrm{~cm}\); m.e.p. \(=5.6\) bar; oil consumption \(=8.16 \mathrm{~kg} / \mathrm{hr} ;\) C.V. \(=42,705\) \(\mathrm{kJ} / \mathrm{kg}\). Determine: (i) mechanical efficiency, (ii) indicated thermal efficiency, and (iii) Brake specific fuel consumption.