Consider the signal:

x(t)=4 sin?(2π80t)+2 sin?(2π130t)+2sin?(2π280)t
Sketch the magnitude spectrum of x(t) showing proper values for the amplitudes.
If that signal is sampled at 600 samples per second, write the expression x(n) of the sampled signals.
Sketch the spectrum of the sampled signal up to 1200 Hz.
If the sampled signal of part b) is filtered by a low pass filter with a 300 Hz cut-off frequency, sketch the magnitude spectrum of the filtered signal
If that signal is sampled at 400 samples per second, write the new expression x(n) of the sampled signals.
Sketch the spectrum of the sampled signal of part e) up to 1000 Hz.
If the sampled signal of part e) is filtered by low pass filter with a 300 Hz cut-off frequency, sketch the magnitude spectrum of the filtered signal