Practice

A food-plant cold room is served by an open-drive compressor operating the R-134a cycle shown (states 1→2→3→4), with $h_1=104$, $h_2=119$, $h_3=41.6$, and $h_4=41.6\,\text{Btu/lb}$. The compressor's electric motor has an efficiency of $0.90$. The cooling coefficient of performance based on the electrical input to the motor is most nearly:

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