In a gas turbine the compressor is driven by the high pressure turbine. the exhaust from the high pressure turbine goes to a free low pressure turbine which runs the load. The air flow rate is 20 kg/s and the minimum and maximum temperatures are respectively 300 K and 1000K. The compressor pressure ratio is 4. Calculate the pressure ratio of the low pressure turbine and the temperature of the exhaust gases from the unit. The compressor and turbine are isentropic. Cp of air and exhaust gases = 1.005 kJ/kgK and g = 1.4.