\textbf{181-} In the circuit shown, what is the input power to the battery of the main branch, in watts?
\textit{[Figure: Circuit with $\varepsilon_1 = 6\,\text{V}$, $r_1 = 1\,\Omega$, $\varepsilon_2 = 12\,\text{V}$, $r_2 = 2\,\Omega$, $r_3 = 2\,\Omega$, two resistors of $2\,\Omega$ and $2\,\Omega$, and $I_1 = \frac{1}{2}\,\text{A}$]}
(1) $7.5$ \quad (2) $6$ \quad (3) $3$ \quad (4) $2.5$