$2)$ A $400-$MVA, $240-$kV$/24-$KV$,$ three$-$phase $\backslash ($ Y $\backslash )-\backslash (\backslash$Delta $\backslash )$ transformer has an equivalent series impedance of $\backslash (1,2+$j $6\backslash$Omega $\backslash )$ per phase referred to the high$-$voltage side. The transformer is supplying a three$-$phase load of $400-$MVA, $0,8$ power factor lagging at a terminal voltage of $24$ kV $($line to line$)$ on its low$-$voltage side. The primary is supplied from a feeder with an impedance of $\backslash (0,6+\backslash$mathrm$\{$j$\}1,2\backslash$Omega $\backslash )$ per phase.

a$.$ Determine the line$-$to$-$line voltage at the high$-$voltage terminals of the transformer and the sending$-$end of the feeder. $(40$ pts $)$

b$.$ With transformer rated values as base quantities, express all impedances in per unit. $(20$ pts$)$

c$.$ Working with per$-$unit values, determine the line$-$to$-$line voltage at the highvoltage terminals of the transformer and the sending$-$end of the feeder. $(20$ pts$)$