
Treat the circle as an ellipse of area $ = \frac{\pi }{4}({P_2} - {P_1})\,({V_2} - {V_1})$
$\Rightarrow \Delta Q = \frac{\pi }{4}\{ (150 - 50) \times {10^3}\} = \frac{\pi }{2}J$
$T_{1}=27^{\circ} C$ [outside fridge]
$T_{2}=-23^{\circ} C$ [inside fridge]
