193. A uniform rod of length $L$ is connected between two sources at temperatures $100\,^\circ\text{C}$ and $0\,^\circ\text{C}$. What fraction $L_1$ of $L$ from the left end should point M be located so that the temperature at point M is 30 degrees Celsius? (Heat exchange between the rod's surface and the environment is neglected.) [Figure: A uniform rod of length $L$ with the left end at $100\,^\circ\text{C}$ and the right end at $0\,^\circ\text{C}$. Point M is located at distance $L_1$ from the left end.]
[(1)] 0.3
[(2)] 0.5
[(3)] 0.7
[(4)] 0.75
\textbf{193.} A uniform rod of length $L$ is connected between two sources at temperatures $100\,^\circ\text{C}$ and $0\,^\circ\text{C}$. What fraction $L_1$ of $L$ from the left end should point M be located so that the temperature at point M is 30 degrees Celsius? (Heat exchange between the rod's surface and the environment is neglected.)
\textit{[Figure: A uniform rod of length $L$ with the left end at $100\,^\circ\text{C}$ and the right end at $0\,^\circ\text{C}$. Point M is located at distance $L_1$ from the left end.]}
\begin{itemize}
\item[(1)] 0.3
\item[(2)] 0.5
\item[(3)] 0.7
\item[(4)] 0.75
\end{itemize}
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