The network admittance matrix of a power system is presented in the following. There are two parallel similar lines between the buses. If one of them is disconnected from bus 1 and then grounded, determine the updated network admittance matrix:

\[
\left[\mathrm{Y}_{\mathrm{Bus}}ight]=\left[\begin{array}{cc}
-j 10 & j 10 \\
j 10 & -j 10
\end{array}ight] \text { p.u. }
\]

1) \(j\left[\begin{array}{cc}-5 & 5 \\ 5 & -10\end{array}ight]\) p.u.
2) \(j\left[\begin{array}{cc}-20 & 20 \\ 20 & -20\end{array}ight]\) p.u.
3) \(j\left[\begin{array}{cc}-20 & 5 \\ 5 & -10\end{array}ight]\) p.и.
4) \(j\left[\begin{array}{cc}-5 & 5 \\ 5 & -5\end{array}ight]\) p.u.