b
(b) \(\because \;\eta  = 1 - \frac{{{T_2}}}{{{T_1}}} = \frac{W}{{{Q_1}}}\)  \({T_2} = 300\,K\)

where \({Q_1} = \) heat absorbed, \({Q_2} = \) heat rejected

==> \(1 - \frac{{T/3}}{T} = \frac{W}{{{Q_1}}}\) ==> \(\frac{2}{3} = \frac{W}{{{Q_1}}} = \frac{{{Q_1} - {Q_2}}}{{{Q_1}}}\)

==> \(\frac{2}{3} = 1 - \frac{{{Q_2}}}{{{Q_1}}}\) ==> \(\frac{{{Q_2}}}{{{Q_1}}} = \frac{1}{3}\) ==> \({Q_2} = \frac{{{Q_1}}}{3} = \frac{Q}{3}\)