N f (kHz) [40p]-1. Amplitude modulation (AM) is applied to a message signal Mf) m(t) to generate amplitude modulated signal Sam(t) with modulation index ma = 0.7. The carrier is c(t) = cos(200000 nt) and amplitude spectrum of the message signal M(f) is depicted in -1 0 1 Fig. 1 Fig.1. (a) Find the amplitude modulated signal Sam(t). (b) Find and draw frequency spectrum of the amplitude modulated signal. Sam (f) =? (c) Design and sketch block diagram of a coherent demodulator to obtain the m(t). (d) Show that with the demodulator designed in 1(c), m(t) can be fully obtained.