A gas turbine develops 120 kj of work while the compressor absorbed 60 kj of work and the heat supplied is 2000kj. If a regenerator which would recover 40% of the heat in the exhaust were used, then the increases in the overall thermal efficiency would be:
(a) 10.2% (b) 8.6%
(c) 6.9% (d) 5.7%