Answer
$T_L=263.5\ K=-9.5°C$
Work Step by Step
From the information given, $T_H=297\ K,\ \dot{W}_i=4\ kW$,
$\dot{Q}_H=3800\ kJ/h\times(297-T_L)$
$COP_{HP}=\dot{Q}_H/\dot{W}_i=\dfrac{1}{1-\frac{T_L}{T_H}}$
Solving for the temperature: $T_L=263.5\ K=-9.5°C$
