$($b$)$ For the circuit shown in Figure $1\mathrm{.}2,$ find an expression for the Norton equivalent resistance, in terms of $\backslash (\backslash$boldsymbol$\{$R$\}\backslash )$ and $\backslash (\backslash$boldsymbol$\{$V$\}\_\{\backslash$boldsymbol$\{$o$\}\}\backslash ),$ across the terminals $\backslash (\backslash$boldsymbol$\{$a$\}\backslash )$ and $\backslash (\backslash$boldsymbol$\{$b$\}\backslash ).$

$[5$ marks$]$

Figure $1\mathrm{.}2$