a) A message signal m (t) has a spectrum M (f) shown below. The message is used to build a signal x (t) = 10[ m(t) + 2 cos(2000 nt)]. The signal x (t) is passed through a nonlinear circuit that has an input-output characteristic of y(t) = x2(t) Plot the spectrum of y(t). where x(t) = A at 100 (Hz) and -100 Hz ) b) The signal y (t) is passed through a frequency-selective filter with frequency response H (f). What should H (f) be so that the output is a double sideband-suppressed carri er (DSB-SC) amplitude- modulated signal? Please plot H(f)