5. An axial flow compressor has an overall pressure ratio of 40 and mass flow of 3 kg/s. If the polytropic efficiency is 88 per cent and the stagnation temperature rise per stage must not exceed 25 K, calculate the number of stages required and the pressure ratio of the first and last stages. Assume equal temperature rise in all stages. If the absolute velocity approaching the last rotor is 165 m/s at an angle of 20° from the axial direction, the work done factor is 0-83, the velocity diagram is symmetrical, and the mean diameter of the last stage rotor is 18 cm, calculate the rotational speed and the length of the last stage rotor blade at inlet to the stage. Ambient conditions are 1-01 bar and 288 K. [7, 1-273, 1-178; 414 rev/s, 1.325 cm] "