A $25$KVA,$\frac{220}{440}V,50Hz$ transformer gave the following test results.

Open circuit test from the low voltage side V$=220$ V$,$ I$=9\mathrm{.}5$ A$,$ P$=650$ W

Short circuit test from the high voltage side V$=37\mathrm{.}5$ V$,$ I$=56\mathrm{.}8$ A$,$ P$=950$ W Calculate:

The equivalent circuit parameters referred to low voltage side.

The low voltage if full load, $0\mathrm{.}8$ lagging power factor is connected to the high voltage side with $440$ V $.$

The voltage regulation at full load with power factor of $0\mathrm{.}8$ lagging.

The efficiency at full load with $0\mathrm{.}8$ lagging power factor.

$5.$ The efficiency at half load with $0\mathrm{.}8$ lagging power factor.