\textbf{185.} In the circuit shown, what voltage does the ideal voltmeter read?
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\textit{[Figure: Circuit with $\varepsilon_1 = 16\,\text{V}$, $r_1 = 2\,\Omega$; $\varepsilon_2 = 6\,\text{V}$, $r_2 = 1\,\Omega$; $\varepsilon_3 = 4\,\text{V}$, $r_3 = 0$; resistors $4\,\Omega$, $5\,\Omega$, $6\,\Omega$, $3\,\Omega$; voltmeter between points $a$ and $b$]}
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(1) $0.6$ \qquad (2) $2.4$ \qquad (3) $5.2$ \qquad (4) $6.4$
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