Answer
See Solution
Work Step by Step
$e=\frac{T_H-T_L}{T_H}$
$e_i=\frac{T_H+10^oC-T_L}{T_H+10^oC}=1-\frac{T_L}{T_H+10^oC}$
$e_d=\frac{T_H-T_L}{T_H}=\frac{T_H-(T_L-10^oC)}{T_H}=1-\frac{T_L-10^oC}{T_H}$
$\frac{T_L-10^oC}{T_H}>\frac{T_L}{T_H+10^oC}$
Decreasing the lower temperature has a large impact on the efficiency.