\textbf{172.} On a winter day, the outdoor temperature is $-5$ degrees Celsius and the indoor temperature is $20$ degrees Celsius. If we increase the indoor temperature by $25$ degrees Celsius and keep it at $25$ degrees Celsius, the rate of heat loss through conduction changes by how much?
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(1) $\dfrac{6}{5}$ \hfill (2) $\dfrac{5}{4}$ \hfill (3) $\dfrac{4}{3}$ \hfill (4) $\dfrac{7}{5}$
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