a. Plot the spectrum of a PAM wave produced by the modulating signal m(t)=A_{m} \cos \left(2 \pi f_{m} t\right) =assuming the modulation frequency fmduration T = 0.45 s.0.2 Hz, sampling period T. = 1s, and pulse b. Using an ideal reconstruction filter, plot the spectrum of the filter output. Compare this result with the output that would be obtained if there were no aperture effect.