Find the air-fuel ratio of a four-stroke, single-cylinder, air-cooled engine with a fuel consumption time for 10 cc as 20.4 s and air consumption time for 0.1 m as 16.3 s. The load is 17 kg at the speed of 3000 rpm. Find the brake specific fuel consumption and brake thermal efficiency. Assume the density of air as 1.175 kg/m and specific gravity of fuel to be 0.7. The lower heating value of fuel is 43MJ/kg and dynamometer constant is 5000.