$5\mathrm{.}4-2$ A periodic square wave m$($t$)($Fig$.$ P$5\mathrm{.}4-2$a$)$ frequency$-$modulates a carrier of frequency f$\_($c$)=$

$10$ kHz with $\backslash$Delta f$=1$kHz$.$ The carricr amplitude is A$.$ The resulting FM signal is demodulated,

as shown in Fig. P$5\mathrm{.}4-2$b by the method discussed in Sec. $5\mathrm{.}4($Fig$.5\mathrm{.}11).$ Sketch the waveforms

at points b$,$c$,$d$,$ and e$.$

$($b$)$