Explanation :
For CE-1 n_{th} = 1 =T_{B}/T_{A} = 1- 500/900 = 0.4444
n_{th }= 1-Q_{2}/Q_{1}
$\therefore$ Q_{2} = (1 - n_{tn}) $\cdot$ Q_{1}
_{ }= ( 1 - 0.4444 ) $\cdot$ 150 = 83.34 MJ
For CE-2 n_{th} = 1 = T_{C}/T_{B} = 1 - 300/500 = 0.4
Q_{4} = (1 - n_{th}) $\cdot$ Q_{3}
= (1 - n_{th) }$\cdot$ Q_{2} ( $\because$ Q_{3} = Q_{2} )
= ( 1 - 0.4) $\cdot$ 83.34
= 50.004 MJ