In the circuit, Vs$1=2$ V$,$ Is$1=7$ A$,$ R$1=8\mathrm{.}5$ Ohm, R$2=5$ Ohm, R$3=6$ Ohm, R$4=2\mathrm{.}5$ Ohm. Use any technique of your choice $($nodal$,$ mesh analysis etc.$)$ to obtain the Thevenin equivalent circuit of the given circuit with respect to terminals $"$a$"$ and $"$b$".$

$1)$ What is the equivalent Thevenin voltage for the circuit?$($Unit: V$)$

$2)$ What is the equivalent Thevenin resistance for the circuit? $($Unit: Ohm$)$

$3)$ What is the resistance of the matching load for this circuit? $($Unit: Ohm$)$

$4)$ What is the power delivered into the matching load for this circuit? $($Unit: W$)$