Find the complex power for the following cases:

$($a$)$ P $=4$ kW$,$ pf $=0\mathrm{.}86($lagging$)$

$($b$)$ S $=2$ kVA, P $=1\mathrm{.}6$ kW $($capacitive$)$

$($c$)$ Vrms $=20820$ V$,$ Irms $=6\mathrm{.}550$ A

$($d$)$ Vrms $=12030$ V$,$ Z $=40+$ j$60$