A three$-$phase, $230$ V$,80$ kVA, $0\mathrm{.}9$ pf $($lagging$)$ load is supplied by three $32$ kVA, $1330/230$ V$,60$ Hz transformers connected in Yd$5$ by means of a common three$-$phase feeder with an impedance of $0\mathrm{.}003+$j$0\mathrm{.}015$ ohms per phase. The transformers are supplied from a three$-$phase source $($substation$)$ through a three$-$phase line with an impedance of $1+$j$6\mathrm{.}6$ ohms per phase. The equivalent impedance $($Rsc$+$jXsc$)$ of one or the single$-$phase transformers referred to the low$-$voltage side is $0\mathrm{.}16+$j$0\mathrm{.}26$ ohms. $($a$)$ Determine the required supply voltage if the load voltage is $230$ V$.($b$)$ Determine the voltage regulation.