Air enters the diffuser of a turbojet engine with a mass flow rate of 85 lb/s at 9 lbf/in^2, 420 R, and a velocity of 750 ft/s. The pressure ratio for the compressor is 12, and its isentropic efficiency is 88%. Air enters the turbine at 2400 R with the same pressure as at the exit of the compressor. Air exits the nozzle at 9 lbf/in^2. The diffuser operates isentropically and the nozzle and the turbine have isentropic efficiencies of 92% and 90% respectively. Neglect kinetic energy except at the diffuser inlet and the nozzle exit. On the basis of air-standard analysis, calculate:
1) the rate of heat addition, in Btu/h.
2) the pressure at the turbine exit, in psi.
3) the compressor power input, in Btu/h.
4) the velocity at the nozzle exit, in ft/s.