During a short$-$circuit test on a $300-$kVA,$5\%$ of normal voltage was necessary to produce full$-$load currents at a power factpr of $0\mathrm{.}23,$ evaluate:

$4\mathrm{.}1$ The percentage resistance $--1-2]\text{'}2]$

$4\mathrm{.}3$ The regulation for a lagging power factor of $0\mathrm{.}8-------------------------[2]$

$4\mathrm{.}6$ The efficiency of the transformer for a lagging power factor of $0\mathrm{.}8$ if the iron loss is $75\%$ of the copper loss

$[2]$