\textbf{169-} The efficiency of a heat engine (Carnot) is 30\%. If the temperature of the hot source is 4 times the temperature of the cold sink, what is the temperature of the cold sink in degrees Celsius?
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(1) $28$ \hspace{2cm} (2) $35.5$ \hspace{2cm} (3) $45.5$ \hspace{2cm} (4) $91$
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