A $\frac{240}{400}-V$ single$-$phase transformer absorbs $35-W$ when its LV winding is connected to a $240-V,50-Hz$ supply, the secondary being open$-$circuit. When the LV winding is short$-$circuited and a $10-V,50-Hz$ supply is connected to HV winding, the power absorbed was $48-W$ and the current in the HV winding is $15-$A$,$ which is the full$-$load current. Calculate the: $(25\mathrm{.}1)$ Full$-$load rating of the transformer $(25\mathrm{.}2)$ Efficiency of the transformer when it delivers $40\%$ of rated kVA at a power tactor of $0\mathrm{.}8$ lagging.