In the circuit below, G$1=25$ mS$,$ G$2=70$ mS$,$ G$3=68$ mS$,$ G$4=30$ mS$,$ G$5=34$ mS$.$

What resistance is measured at the terminals of the network below if the switch is:

$($a$)$ open $($open circuit$)$

$($b$)$ closed $($short circuit$)$

$($c$)$ replaced by a $28$ mS conductance