$7\mathrm{.}23$ Determine the instantaneous time functions corresponding

to the following phasors:

$($a$)$ I$1=6$e j$60$

A at f$=60$ Hz$446$

$($b$)$ I$2=2$e$$ j$30$ A at f$=1$ kHz

$*($c$)$ I$3=$ j$3$ A at f$=1$ MHz

$($d$)$ I$4=(3+$ j$4)$ A at f$=10$ kHz

$($e$)$ I$5=4120$ A at f$=3$ MHz