A turbofan engine has a fan and low-pressure compressor driven by the low-pressure turbine. It operates at a flight velocity of 200 m/s at 12,000 m altitude, where the ambient temperature and pressure are 216.65 K and 0.1933 bar respectively. The overall pressure ratio of the engine is 19, the fan and low pressure compressor pressure ratios are 1.65 and 2.5 respectively. The fan, compressors and turbines have a 90% polytrophic efficiency. Assume an isentropic inlet and separate isentropic convergent nozzles, a fuel heating value of 43,000 kJ/kg and a combustor total pressure loss of 6.5%. Determine the core engine and by-pass duct exit velocities, the engine thrust specific fuel consumption, thrust and specific thrust for an engine inlet air flow of 100 kg/s and by-pass ratio of 3.0. Determine whether the nozzles are choked.