Answer
Valid
Work Step by Step
$\eta_{max}=1-\dfrac{T_L}{T_H}$
Given $T_L=490°R,\ T_H=920°R$
$\eta_{max}=0.467$
$\dot{Q}_H=\dot{W}_e+\dot{Q}_L$
Given $\dot{W}_e=4.5\ hp,\ \dot{Q}_L=15000\ Btu/h$
$\dot{Q}_H=26450\ Btu/h$
$\eta = \dot{W}_e/\dot{Q}_H$
$\eta=0.433$
Valid