\textbf{183-} In the circuit shown, when both switches are open or both are closed, the ammeter reads $0.2\,\text{A}$. What is the resistance $R$?
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\textit{[Figure: Circuit with resistors $30\,\Omega$, $40\,\Omega$, $30\,\Omega$, switches $k_1$ and $k_2$, resistor $R$, battery $\varepsilon$ with internal resistance $r = 10\,\Omega$.]}
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(1) $60$ \hfill (2) $40$ \hfill (3) $15$ \hfill (4) $10$
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