A two-port network shown below is excited by external $dc$ sources. The voltages and the currents are measured with voltmeters $\mathrm{V}_{1}, \mathrm{~V}_{2}$ and ammeters $\mathrm{A}_{1}, \mathrm{~A}_{2}$ (all assumed to be ideal), as indicated. Under following switch conditions, the readings obtained are:
- $\mathrm{S}_{1}-$ Open, $\mathrm{S}_{2}-$ Closed $ \quad \mathrm{A}_{1}=0 \mathrm{~A}, \mathrm{~V}_{1}=4.5 \mathrm{~V}, \mathrm{~V}_{2}=1.5 \mathrm{~V}, \mathrm{~A}_{2}=1 \mathrm{~A}$
- $\mathrm{S}_{1}-$ Closed, $\mathrm{S}_{2}-$ Open $ \quad \mathrm{A}_{1}=4 \mathrm{~A}, \mathrm{~V}_{1}=6 \mathrm{~V}, \mathrm{~V}_{2}=6 \mathrm{~V}, \mathrm{~A}_{2}=0 \mathrm{~A}$
The $\text{z}$-parameter matrix for this network is
- $\left[\begin{array}{ll}1.5 & 1.5 \\ 4.5 & 1.5\end{array}\right]$
- $\left[\begin{array}{ll}1.5 & 4.5 \\ 1.5 & 4.5\end{array}\right]$
- $\left[\begin{array}{ll}1.5 & 4.5 \\ 1.5 & 1.5\end{array}\right]$
- $\left[\begin{array}{ll}4.5 & 1.5 \\ 1.5 & 4.5\end{array}\right]$