Three single$-$phase, $45$ kVA, $2300/230$ V$,60$ Hz transformers are connected to form a three$-$phase, $4000/230$ V transformer bank. The equivalent impedance of each transformer referred to low voltage is $0\mathrm{.}06+$j$0\mathrm{.}1$ ohms. The three$-$phase transformer supplies a three$-$phase, $115$ kVA, $230$ V$,0\mathrm{.}63$ lagging$-$power$-$factor load.$($a$)$ Determine the transformer winding currents. $($b$)$ Determine the primary voltage $($line$-$to$-$line$)$ required. $($c$)$ Determine the voltage regulation.