Consider a Brayton cycle and assume variable specific heats for air. Air enters the compressor of a gas-turbine engine at 300 K and 100 kPa, where it is compressed to 700 kPa and 580 K. Heat is transferred to air in the amount of 950 kJ/kg before it enters the turbine. For a turbine efficiency of 86%, determine (a) the fraction of the turbine work output used to drive the compressor and (b) the thermal efficiency.