A continuous$-$time signal x$($t$)$ is obtained at the output of an ideal lowpass filter with cutoff frequency c $=10,000$$.$ If impulse train sampling is performed on x$($t$),$ which of the following sampling periods would guarantee that x$($t$)$ can be recovered from its sampled version using an appropriate lowpass filter? $($a$)$ T$=0\mathrm{.}5$x$10-3($b$)$ T$=2$x$10-3($c$)$ T$=10-4$