A heat engine receives heat from a source at $1500 \mathrm{~K}$ at a rate of $600 \mathrm{~kJ} / \mathrm{s}$ and rejects the waste heat to a sink at $300 \mathrm{~K}$. If the power output of the engine is $400 \mathrm{~kW},$ the second-law efficiency of this heat engine is
(a) $42 \%$
(b) $53 \%$
(c) $83 \%$
(d) $67 \%$
(e) $80 \%$