A Four-cylinder petrol engine has an output of 52 kW at 2000 rev/min. A Morse test is carried out and the brake torque readings are 177, 170, 168, and 174 N m respectively. For normal running at this speed the specific fuel consumption is 0.364 kg/kW h. The of the fuel is 44 2(0 kJ" kg. Calculate the mechanical and brake thermal efficiencies of the engine.